<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>010950 - Disclosure - Trust Preferred Securities</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

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</LabelSeparator><Level>1</Level><ElementName>bmnm_TrustPreferredSecuritiesAbstract</ElementName><ElementPrefix>bmnm_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Trust Preferred Securities [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>bmnm_TrustPreferredSecuritiesTextblock</ElementName><ElementPrefix>bmnm_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>verboseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="FROM_Jan01_2013_TO_Jun30_2013" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;font-weight:bold;margin-left:0px;"&gt;NOTE 6&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;font-weight:bold;"&gt;.&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;font-weight:bold;"&gt;  TRUST PREFERRED SECURITIES&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;margin-left:18px;"&gt;During 2005, &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;Bimini Capital sponsored &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;the formation of a &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;statutory trust, known as Bimini Capital Trust II (&amp;#8220;BCTII&amp;#8221;) of which 100% of the common eq&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;uity is owned by Bimini Capital.  It was&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; formed for the purpose of issuing trust preferred capital securities to third-party investors and investing the proceeds from the sale of such capital securities solely in junior subordinated debt securities of Bimini Capital. The debt securities held by &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;BCTII&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; are the sole assets of &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;BCTII&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;margin-left:18px;"&gt;As of &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;June 30, 2013&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; and &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;December 31, 2012&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;,&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; the outstanding principal balance on the junior subordinated debt securities owed to BCTII &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;was&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; $26.8 million.  The BCTII trust preferred securities and Bimini Capital's BCTI&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;I Junior Subordinated Notes have&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; a rate of interest that floats at a spread of 3.50% over the prevailing three-month LIBOR rate.  &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;As of &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;June 30, 2013&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;, the interest rate was &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;3.77%&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;.&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; The BCTII trust preferred securities and Bimini Capital's BCTII Junior Subordinated Notes require quarterly interest distributions and are redeemable at Bimini Capital's option, in whole or in part and without penalty, beginning December 15, 2010. Bimini Capital's BCTII Junior Subordinated Notes are subordinate and junior in right of payment of all present and future senior indebtedness. &lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;margin-left:18px;"&gt;The trust is a VIE&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; because the holders of the equity investment at risk do not have adequate decision making ability over the trust's activities. Since Bimini Capital's investment in the trust's common equity securities was financed directly by the applicable trust as a result of its loan of the proceeds to Bimini Capital, that investment is not considered to be an equity investment at risk. Since Bimini Capital's common share investment in BCTII &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;is&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; not a &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;variable interest, Bimini Capital is not the primary beneficiary of &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;BCTII&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;. Therefore, Bimini Capital has not consolidated the financial statements of BCTII into its financial statements.&lt;/font&gt;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&amp;#160;&lt;/p&gt;&lt;p style='margin-top:0pt; margin-bottom:0pt'&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;margin-left:18px;"&gt;The accompanying consolidated financial statements present Bimini Capital's BCTII Junior Subordinated Notes issued to the trust as a liability and Bimini Capital's investment in the common equity securities of BCTII as an asset&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; (in&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;cluded in&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; prepaid expenses and other assets, net)&lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;. &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt; &lt;/font&gt;&lt;font style="font-family:Arial Narrow;font-size:11pt;"&gt;For financial statement purposes, Bimini Capital records payments of interest on the Junior Subordinated Notes issued to BCTII as interest expense.&lt;/font&gt;&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>No authoritative reference available.</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Trust Preferred Securities</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>Trust Preferred Securities</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://www.biminicapital.com/role/DisclosureTrustPreferredSecurities</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
