Exhibit 99.1

STARENT NETWORKS, CORP. REPORTS SECOND QUARTER 2009 FINANCIAL RESULTS

TEWKSBURY, Mass. — July 23, 2009 — Starent Networks, Corp. (Nasdaq: STAR), a leading provider of infrastructure solutions that enable mobile operators to deliver multimedia services, today reported financial results for the second quarter ended June 30, 2009. Net revenues for the second quarter of 2009 were $78.3 million, compared to net revenues of $61.2 million for the second quarter of 2008. Net revenues for the six months ended June 30, 2009 were $151.5 million, compared to $117.4 million for the same period in 2008.

The company’s income before tax expense in the second quarter of 2009 was $24.4 million, an increase of 61% from the second quarter of 2008. Income before tax expense for the six months ended June 30, 2009 was $45.6 million, an increase of 81% from the same period in 2008.

The company’s tax rate was 37.7% for the second quarter of 2009, and 38.6% for the six months ended June 30, 2009, reflecting normal provisions for income taxes. This compares to a tax rate of 8.9% for the second quarter of 2008 and 7.1% for the six months ended June 30, 2008, which did not reflect normal tax provisions due to the company’s use of net operating loss carryforwards in determining the tax provision for those periods.

Net income for the second quarter of 2009 was $15.2 million, or $0.20 per diluted share, compared to net income of $13.8 million, or $0.19 per diluted share, for the second quarter of 2008. Second quarter 2009 results included $5.6 million of non-cash stock-based compensation expenses compared to similar expenses of $4.5 million in the second quarter of 2008. Net income for the six months ended June 30, 2009 was $28.0 million, or $0.37 per diluted share, compared to $23.4 million, or $0.32 per diluted share, for the same period in 2008. The results for the first six months of 2009 included $9.6 million of non-cash stock-based compensation expenses compared to similar expenses of $7.9 million in the same period of 2008.

Excluding the impact of stock-based compensation, non-GAAP net income for the second quarter of 2009 was $18.8 million, or $0.25 per diluted share, compared to non-GAAP net income for the second quarter of 2008 of $18.3 million, or $0.25 per diluted share. Non-GAAP net income for the six months ended June 30, 2009 was $34.9 million, or $0.46 per diluted share, compared to non-GAAP net income of $31.3 million, or $0.42 per diluted share, for the same period in 2008.

Operational Highlights

Highlights for the second quarter 2009 included:

• Introduction of Starent’s new processing card, the Packet Services Card 2 (PSC2), and 10 Gigabit Ethernet (10GE) line card to increase the market leading performance of its ST40^™ platform by up to 4X.

- more -

• Selection by Cox Communications, the third largest cable provider in the United States, as a multimedia core vendor for its wireless network.

• Selection of Starent Networks’ Security Gateway by KDDI for secure Wi-Fi access over its fixed broadband networks, allowing subscribers to benefit from seamless service experiences as they roam between un-secure Wi-Fi networks and secure EV-DO networks.

• Inclusion of Starent Networks’ Femtocell Gateway in the industry’s first interoperability demonstration of the new 3GPP luh standard, which is critical to successfully bringing femtocells to mass market.

Conference Call Information

Date: July 23, 2009

Time: 5:00 p.m. Eastern time

Toll-free North America: 888-679-8037

International dial-in number: 617-213-4849

Passcode: 36031653

Live webcast: Available at http://ir.starentnetworks.com

A telephone replay of the call will be available following the conference call through July 30, 2009. To access the replay, parties in the United States and Canada should call 888-286-8010 and parties outside of the United States and Canada should call 617-801-6888. The passcode for the replay is 96583811. An archived version of the webcast will be available until September 30, 2009 on the company’s website at http://ir.starentnetworks.com.

About Starent Networks

Starent Networks, Corp. is a leading provider of infrastructure solutions that enable mobile operators to deliver multimedia services to their subscribers. Starent Networks has created solutions that provide mobile operators with the functions and services needed for access, mobility management and call control in their networks. Through integrated intelligence and high performance capabilities, Starent Networks’ solutions also enhance subscriber management, billing and session policy enforcement. The company’s products are capable of supporting a wide range of mobile wireless networks, such as CDMA2000, UMTS/HSPA, LTE, WiFi, and WiMAX. Starent Networks’ products have been deployed by over 95 mobile operators in over 40 countries. Additional information about Starent Networks is available at www.starentnetworks.com.

Forward Looking Statements

Statements contained in this release that are not historical fact may be forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Such forward-looking statements may relate, among other things, to: our position in the multimedia core network platform market; our expected financial and operating results; the amount and impact of stock-based compensation charges; our definition of “non-GAAP net income” and/or “non-GAAP net income per share”; our ability to build and expand deployments; the benefits of our products and services; and our ability to achieve our goals, plans and objectives. Such forward-looking statements do not constitute guarantees of future performance and are subject to a variety of risks and uncertainties that could cause our actual results to differ materially from those anticipated. These forward-looking statements involve risks and uncertainties, as well as assumptions that, if they do not fully materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such

- more—

forward-looking statements. The risks and uncertainties that could cause our results to differ materially from those expressed or implied by such forward-looking statements include our ability to react to trends and challenges in our business and the markets in which we operate; our ability to anticipate market needs or develop new or enhanced products to meet those needs; the adoption rate of our products; our ability to establish and maintain successful relationships with our distribution partners; our reliance on a limited number of customers for a substantial portion of our revenue; the timing of product releases or upgrades by us or by our competitors; our reliance on a single product line focused on a single market; our ability to compete in our industry; fluctuations in demand, sales cycles and prices for our products and services; our ability to penetrate the GSM/UMTS market; shortages or price fluctuations in our supply chain; our ability to protect our intellectual property rights; general political, economic and market conditions and events; and other risks and uncertainties described more fully in our documents filed with or furnished to the Securities and Exchange Commission. More information about these and other risks that may impact our business are set forth in our most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q, each of which are filed with the SEC. In addition, the forward-looking statements included in this press release represent Starent Networks’ views as of the date of this press release. Starent Networks anticipates that subsequent events and developments will cause its views to change. While Starent Networks may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing Starent Networks’ views as of any date subsequent to the date of this press release.

Non-GAAP Financial Measures

In addition to disclosing financial measures prepared in accordance with Generally Accepted Accounting Principles (GAAP), this press release and the accompanying tables contain non-GAAP financial measures. For a description of these non-GAAP financial measures, including the reasons why management uses each measure, and reconciliations of these non-GAAP financial measures to the most directly comparable GAAP financial measures, please see the section of the accompanying table titled “Use of Non-GAAP Financial Information” as well as the related table that follows it.

A copy of this press release can be found on the investor relations page of Starent Networks’ website at http://ir.starentnetworks.com.

# # #

Starent^®, ST40, and the Starent Networks logo are either registered trademarks or trademarks of Starent Networks, Corp. in the United States and/or other countries.

Starent Networks, Corp.

Condensed Consolidated Balance Sheets

(in thousands)

	June 30,			December 31,
	2009			2008
Assets	(unaudited)
Current assets:
Cash and cash equivalents	$	389,913		$	369,351
Accounts receivable		54,910			53,689
Inventories		50,446			48,734
Deferred tax assets, net		9,173			3,449
Prepaid expenses and other current assets		7,574			4,709
Total current assets		512,016			479,932
Property and equipment, net		36,258			29,632
Deferred tax assets, net		13,287			9,699
Other assets		8,975			8,011
Restricted cash		822			943
Total assets	$	571,358		$	528,217
Liabilities and stockholders’ equity
Current liabilities:
Accounts payable	$	9,361		$	9,042
Accrued expenses and other current liabilities		20,131			23,359
Accrued income taxes		10,922			1,945
Current portion of deferred revenue		139,604			141,726
Total current liabilities		180,018			176,072
Deferred revenue, net of current portion		6,995			10,959
Other long-term liabilities		2,842			2,985
Stockholders’ equity:
Common stock		71			70
Additional paid-in capital		387,002			371,655
Accumulated deficit		(5,570	)		(33,524	)
Total stockholders’ equity		381,503			338,201
Total liabilities and stockholders’ equity	$	571,358		$	528,217

Starent Networks, Corp.

Condensed Consolidated Statements of Operations

(in thousands, except per share data)

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2009			2008			2009			2008
	(unaudited)						(unaudited)
Revenues:
Product	$	65,829		$	52,160		$	128,959		$	101,047
Service		12,490			9,008			22,562			16,349
Total revenues		78,319			61,168			151,521			117,396
Cost of revenues:
Product		9,843			9,497			19,611			18,546
Service		6,006			3,806			10,552			7,716
Total cost of revenues		15,849			13,303			30,163			26,262
Gross profit		62,470			47,865			121,358			91,134
Operating expenses:
Research and development		16,549			12,500			30,586			24,843
Sales and marketing		16,864			16,173			33,332			35,024
General and administrative		6,691			5,931			13,377			11,087
Total operating expenses		40,104			34,604			77,295			70,954
Income from operations		22,366			13,261			44,063			20,180
Other income (expense), net		2,012			1,861			1,492			5,044
Income before income tax expense		24,378			15,122			45,555			25,224
Income tax expense		(9,202	)		(1,346	)		(17,601	)		(1,795	)
Net income	$	15,176		$	13,776		$	27,954		$	23,429
Net income per common share:
Basic	$	0.21		$	0.20		$	0.40		$	0.34
Diluted	$	0.20		$	0.19		$	0.37		$	0.32
Weighted-average shares outstanding used in computing net income per common share:
Basic		70,648			69,379			70,367			69,105
Diluted		75,841			74,407			75,214			74,372
Stock-based compensation included in the lines above:
Cost of revenues	$	545		$	381		$	893		$	694
Research and development		1,987			1,803			3,387			3,107
Sales and marketing		1,750			1,366			2,995			2,293
General and administrative		1,361			968			2,360			1,794
	$	5,643		$	4,518		$	9,635		$	7,888

Use of Non-GAAP Financial Information

To supplement our condensed consolidated financial statements presented on a GAAP basis, Starent Networks uses non-GAAP measures of operating results, net income and net income per share, which are adjusted to exclude stock-based compensation expense and the related income tax effect. We believe these adjustments are appropriate to enhance an overall understanding of our past financial performance and also our prospects for the future. These adjustments to our current period GAAP results are made with the intent of providing both management and investors a more complete understanding of Starent Networks’ underlying operating results and trends and our marketplace performance. The non-GAAP results are an indication of our baseline performance that are considered by management for the purpose of making operational decisions. In addition, these adjusted non-GAAP results are the primary indicators management uses as a basis for planning and forecasting future periods. The presentation of this additional information is not meant to be considered in isolation or as a substitute for net income or basic and diluted net income per share prepared in accordance with generally accepted accounting principles in the United States. Non-GAAP financial measures are not based on a comprehensive set of accounting rules or principles and are subject to limitations.

Starent Networks, Corp.

Reconciliation of GAAP to Non-GAAP Items

(in thousands, except per share data)

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2009			2008			2009			2008
	(unaudited)						(unaudited)
Gross profit
Total revenues	$	78,319		$	61,168		$	151,521		$	117,396
Total cost of revenues		15,849			13,303			30,163			26,262
Gross profit	$	62,470		$	47,865		$	121,358		$	91,134
Adjustments to reconcile to Non-GAAP gross profit: Stock-based compensation		545			381			893			694
Non-GAAP gross profit	$	63,015		$	48,246		$	122,251		$	91,828
Operating expenses:
Research and development	$	16,549		$	12,500		$	30,586		$	24,843
Sales and marketing		16,864			16,173			33,332			35,024
General and administrative		6,691			5,931			13,377			11,087
Total operating expenses	$	40,104		$	34,604		$	77,295		$	70,954
Adjustments to reconcile to Non-GAAP operating expenses:
Stock-based compensation included in:
Research and development	$	1,987		$	1,803		$	3,387		$	3,107
Sales and marketing		1,750			1,366			2,995			2,293
General and administrative		1,361			968			2,360			1,794
Non-GAAP operating expenses:
Research and development	$	14,562		$	10,697		$	27,199		$	21,736
Sales and marketing		15,114			14,807			30,337			32,731
General and administrative		5,330			4,963			11,017			9,293
Non-GAAP operating expenses	$	35,006		$	30,467		$	68,553		$	63,760
Income from operations	$	22,366		$	13,261		$	44,063		$	20,180
Adjustments to reconcile to Non-GAAP income from operations:
Stock-based compensation		5,643			4,518			9,635			7,888
Non-GAAP income from operations	$	28,009		$	17,779		$	53,698		$	28,068
Income tax expense:
Income tax expense	$	(9,202	)	$	(1,346	)	$	(17,601	)	$	(1,795	)
Adjustments to reconcile to Non-GAAP income tax expense:
Income tax effect		(2,038	)		—			(2,739	)		—
Non-GAAP income tax expense	$	(11,240	)	$	(1,346	)	$	(20,340	)	$	(1,795	)

	Three Months Ended					Six Months Ended
	June 30,					June 30,
	2009			2008		2009			2008
	(unaudited)					(unaudited)
GAAP net income	$	15,176		$	13,776	$	27,954		$	23,429
Adjustments to reconcile to Non-GAAP net income:
Stock-based compensation (1)		5,643			4,518		9,635			7,888
Income tax effect (2)		(2,038	)		—		(2,739	)		—
Non-GAAP net income	$	18,781		$	18,294	$	34,850		$	31,317
Non-GAAP net income per common share	$	0.25		$	0.25	$	0.46		$	0.42
Weighted-average shares used in computing net income per common share:
Diluted		75,841			74,407		75,214			74,372

(1) Adjustment for stock-based compensation expense. Stock-based compensation expense is a non-cash expense accounted for in accordance with the fair value provisions of Statement of Financial Accounting Standards No. 123(R) (SFAS 123(R)). While stock-based compensation is a large component of our expense, we believe investors prefer to exclude the effects of stock-based compensation expense in order to compare our financial performance with that of other companies and between time periods.

(2) Income tax effect of excluding stock-based compensation. There was no adjustment for the comparable period in 2008.

Contact:

Mark Donohue

Director, Investor Relations and Assistant Treasurer

Starent Networks, Corp.

http://ir@starentnetworks.com

978-863-3743