EXHIBIT 99.1

United Security Bancshares Appoints Two New Members to Board of Directors

FRESNO, CA, November 29, 2017. United Security Bancshares (http://www.unitedsecuritybank.com/) (Nasdaq Global Select: UBFO) announced the appointment of Nabeel Mahmood and Brian Tkacz to the Company's Board of Directors. Mr. Mahmood and Mr. Tkacz will also serve on the Board of United Security Bank, a wholly-owned subsidiary of United Security Bancshares.

Dennis R. Woods, President and Chief Executive Officer of the Company, stated “We are delighted to welcome Brian and Nabeel to our Board and look forward to the fresh perspectives they will bring to our meetings. Both are highly qualified and have an extensive background in information technology which complements the knowledge and experience of our current Board."

Nabeel Mahmood brings over 18 years of executive level information technology experience to the Board. Nabeel is the current Chief Information Technology Officer for Maxco and was previously the Chief Information Officer for KamWay.

Brian Tkacz graduated from Cornell University, and later earned his MBA at the University of Virginia, Darden Graduate School of Business. Brian is currently the Director of Information Technology for Markel Corporation and was previously the Director of Consumer Lending for Capital One.

Mr. Mahmood has been appointed to the Company's Audit Committee and Mr. Tkacz has been appointed to the Bank's Risk Management Committee.

United Security Bancshares (NASDAQ: UBFO) is the holding company for United Security Bank, which was founded in 1987. United Security Bank is headquartered in Fresno and operates 11 full-service branch offices in Fresno, Bakersfield, Campbell, Caruthers, Coalinga, Firebaugh, Oakhurst, San Joaquin, and Taft. Additionally, United Security Bank operates Commercial Real Estate Construction, Commercial Lending, Consumer Lending, and Financial Services departments. For more information, please visit www.unitedsecuritybank.com.

FORWARD-LOOKING STATEMENTS

This news release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended and the Company intends such statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. Forward-looking statements are based on management’s knowledge and belief as of today and include information concerning the Company’s possible or assumed future financial condition, and its results of operations, business and earnings outlook. These forward-looking statements are subject to risks and uncertainties. A number of factors, some of which are beyond the Company’s ability to control or predict, could cause future results to differ materially from those contemplated by such forward-looking statements. These factors include (1) changes in interest rates, (2) significant changes in banking laws or regulations, (3) increased competition in the company’s market, (4) other-than-expected credit losses, (5) earthquake or other natural disasters impacting the condition of real estate collateral, (6) the effect of acquisitions and integration of acquired businesses, (7) the impact of proposed and/or recently adopted changes in laws, and regulations on the Company and its business; (8) changing bank regulatory conditions, policies, whether arising as new legislation or regulatory initiatives or changes in our regulatory classifications, that could lead to restrictions on activities of banks generally or as to the Bank, including specifically the formal order between the Federal Reserve Bank of San Francisco and the Company and the Bank, (9) failure to comply with the written regulatory agreement under which the Company is subject and (10) unknown economic impacts caused by the State of California’s budget issues, including the effect on Federal spending do to sequestration required by the Budget Control Act of 2011. Management cannot predict at this time the severity or duration of the effects of the recent business slowdown on the Company's specific business activities and profitability. Weaker or a further decline in capital and consumer spending, and related recessionary trends could adversely affect the Company's performance in a number of ways including decreased demand for our products and services and increased credit losses. Likewise, changes in interest rates, among other things, could slow the rate of growth or put pressure on current deposit levels and affect the ability of borrowers to repay loans. Forward-looking statements speak only as of the date they are made, and the Company does not undertake to update forward-looking statements to reflect circumstances or events that occur after the date the statements are made, or to update earnings guidance including the factors that influence earnings. For a more complete discussion of these risks and uncertainties, see the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, and particularly the section of Management’s Discussion and Analysis. Readers should carefully review all disclosures the Company files from time to time with the Securities and Exchange Commission ("SEC").