Exhibit 99.1

For Immediate Release

Investar Holding Corporation Announces 2015 First Quarter Results

BATON ROUGE, LA (April 28, 2015) – Investar Holding Corporation (NASDAQ: ISTR) (the “Company”), the holding company for Investar Bank, today announced financial results for the quarter ended March 31, 2015. For the quarter ended March 31, 2015, the Company reported net income of $2.0 million, or $0.27 per diluted share, compared to $0.9 million, or $0.21 per diluted share for the quarter ended March 31, 2014. This represents an increase of $1.1 million, or 122%, in net income. For the quarter ended March 31, 2015, net income and diluted earnings per share increased $0.5 million, or 31.5%, and $0.07, respectively, when compared to the quarter ended December 31, 2014, after adjusting for the net effect of an investment in a tax credit entity.

Investar Holding Corporation President and Chief Executive Officer John D’Angelo said:

“We continue to grow into our staffing and facility infrastructure, allowing us to realize significant improvement in both return on assets and efficiency ratios. Noninterest expenses remained relatively flat compared to the latter half of 2014 with the exception of seasonal increases in benefit costs. We continued to make significant progress in the first quarter of 2015, growing both our commercial and industrial loan portfolio and noninterest bearing deposits. We believe growth in these areas increases the value of our franchise and will remain a primary focus.”

Performance Highlights

Consumer loans, including consumer loans held for sale, totaled $175.8 million at March 31, 2015, a decrease of $38.2 million, or 17.9% from $214.0 million at December 31, 2014. The decrease is mainly attributable to the $37.7 million decrease in the balance of consumer loans held for sale at March 31, 2015 when compared to December 31, 2014. Two consumer loan sales were postponed by the buyer from the fourth quarter of 2014 to the first quarter of 2015, therefore increasing the balance of consumer loans held for sale at December 31, 2014.

At March 31, 2015, the Company’s total business lending portfolio, which consists of loans secured by owner occupied commercial real estate properties and commercial and industrial loans, was $183.0 million, an increase of $9.1 million, or 5.3%, compared to the business lending portfolio of $173.9 million at December 31, 2014.

Management continues to monitor the Company’s loan portfolio for exposure, directly or indirectly, to the potential negative impacts from the fluctuation in oil and gas prices. Less than 1% of the total loan portfolio remains directly related to the energy sector. At March 31, 2015, none of these loans were past due. At this time, management does not anticipate that decreases in oil and gas prices will negatively impact borrowers’ ability to service their debt. Management continually evaluates the allowance for loan losses based on several factors, including economic conditions, and currently believes that any potential negatively affected future cash flows related to these loans would be covered by the allowance for loan losses.

The provision for loan loss expense was $0.7 million for the first quarter of 2015, an increase of $0.5 million compared to the first quarter of 2014. The allowance for loan losses was $5.4 million, or 178.42% and 0.83% of nonperforming loans and total loans, respectively, at March 31, 2015, compared to $4.6 million, or 138.61% and 0.74% of nonperforming loans and total loans, respectively, at December 31, 2014.

Deposits

Total deposits at March 31, 2015 were $698.9 million, an increase of $70.8 million, or 11.3%, from December 31, 2014. The increase in total deposits was driven primarily by an increase of $14.2 million, or 20.2%, in noninterest bearing demand deposits, an increase in NOW accounts of $28.5 million, or 24.5%, and an increase in time deposits of $19.4 million, or 6.3%, from December 31, 2014. The Company’s deposit cross sell strategy, as well as management’s focus on growing the commercial and industrial loan portfolio and bringing in related deposits, continues to positively impact both noninterest bearing demand deposit and NOW account growth.

The following table sets forth the composition of the Company’s deposits as of the dates indicated (dollars in thousands):

Net Interest Income

Net interest income for the first quarter of 2015 totaled $7.5 million, an increase of $1.6 million, or 27.8%, from the first quarter of 2014. The increase was a direct result of continued growth of the Company’s loan portfolio with an increase in net interest income of $2.1 million due to an increase in volume offset by a $0.5 million decrease related to a reduction in yield when compared to the first quarter of 2014.

The Company’s net interest margin was 3.71% for the quarter ended March 31, 2015 compared to 3.84% for the fourth quarter of 2014 and 3.93% for the first quarter of 2014. The Company now sells, and plans to continue to sell, the majority of the consumer loans that it originates. Consumer loan fees previously recognized as a component of interest income are now included in noninterest income, impacting the yield realized on the consumer loan portfolio. The yield on interest earning assets was 4.35% for the quarter ended March 31, 2015 compared to 4.47% for the fourth quarter of 2014 and 4.65% for the first quarter of 2014. Including consumer loan fees in interest income in the current quarter would result in a net interest margin and yield on interest earning assets of 3.82% and 4.46%, respectively, which is comparable to the net interest margin and yield on interest earning assets of 3.84% and 4.47%, respectively, recognized in the fourth quarter of 2014. The cost of deposits increased two basis points when comparing the first quarter of 2015 to the fourth quarter of 2014 and declined one basis point when comparing the first quarter of 2015 to the first quarter of 2014.

Noninterest Income

Noninterest income for the first quarter of 2015 totaled $2.5 million, an increase of $1.5 million, or 138.3%, compared to the first quarter of 2014. The increase resulted primarily from the $1.1 million increase in the gain on sale of loans. For the first quarter of 2015, $1.2 million and $0.5 million was recognized as gain on sales of our consumer and mortgage loans, respectively. Fee income on loans held for sale increased $0.2 million primarily as a result of the change in strategy for our consumer loan portfolio, discussed above. Prior to this shift in strategy, consumer loan fees were included in interest income.

Noninterest Expense

Noninterest expense for the first quarter of 2015 totaled $6.4 million, an increase of $1.0 million, or 19.3%, compared to the first quarter of 2014. The increase in noninterest expense is primarily due to the $0.4 million increase in salaries and employee benefits and the $0.3 million increase in other operating expenses, both of which are primarily attributable to the opening of the Highland Road branch in Baton Rouge, Louisiana on August 1, 2014 and the addition of 10 full-time equivalent employees.

Basic Earnings Per Share and Diluted Earnings Per Share

The Company reported both basic earnings per share and diluted earnings per share of $0.27 for the three months ended March 31, 2015, an increase of $0.04 and $0.06, respectively, when compared to basic and diluted earnings per share for the three months ended March 31, 2014.

Taxes

The Company recorded income tax expense of $1.0 million for the quarter ended March 31, 2015, which equates to an effective tax rate of 33.1%.

About Investar Holding Corporation

Investar Holding Corporation, headquartered in Baton Rouge, Louisiana, provides full banking services, excluding trust services, through its wholly-owned banking subsidiary, Investar Bank, a state chartered bank. The Company’s primary market is South Louisiana and it currently operates 11 full service banking offices located throughout its market. At March 31, 2015, the Company had 177 full-time equivalent employees.

Non-GAAP Financial Measures

This press release contains financial information determined by methods other than in accordance with generally accepted accounting principles in the United States of America, or GAAP. These measures and ratios include “tangible book value,” “tangible book value per common share,” “efficiency ratio,” “tangible equity to tangible assets,” “adjusted efficiency ratio,” “adjusted return on equity,” and “adjusted net income.” Management believes these non-GAAP financial measures provide information useful to investors in understanding the Company’s financial results, and the Company believes that its presentation, together with the accompanying reconciliations, provide a more complete understanding of factors and trends affecting the Company’s business and allow investors to view performance in a manner similar to management, the entire financial services sector, bank stock analysts and bank regulators. These non-GAAP measures should not be considered a substitute for GAAP basis measures and results, and the Company strongly encourages investors to review its consolidated financial statements in their entirety and not to rely on any single financial measure. Because non-GAAP financial measures are not standardized, it may not be possible to compare these financial measures with other companies’ non-GAAP financial measures having the same or similar names. A reconciliation of the non-GAAP financial measures disclosed in this press release to the comparable GAAP financial measures is included at the end of the financial statement tables.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that reflect the Company’s current views with respect to, among other things, future events and financial performance. The Company generally identifies forward-looking statements by terminology such as “outlook,” “believes,” “expects,” “potential,” “continues,” “may,” “will,” “could,” “should,” “seeks,” “approximately,” “predicts,” “intends,” “plans,” “estimates,” “anticipates,” or the negative version of those words or other comparable words. Any forward-looking statements contained in this press release are based on the historical performance of the Company and its subsidiaries or on the Company’s current plans, estimates and expectations. The inclusion of this forward-looking information should not be regarded as a representation by the Company that the future plans, estimates or expectations by the Company will be achieved. Such forward-looking statements are subject to various risks and uncertainties and assumptions relating to the Company’s operations, financial results, financial condition, business prospects, growth strategy and liquidity. If one or more of these or other risks or uncertainties materialize, or if the Company’s underlying assumptions prove to be incorrect, the Company’s actual results may vary materially from those indicated in these statements. These factors should not be construed as exhaustive. The Company does not undertake any obligation to publicly update or review any forward-looking statement, whether as a result of new information, future developments or otherwise. A number of important factors could cause actual results to differ materially from those indicated by the forward-looking statements. Information on these factors can be found in the filings that the Company makes with the Securities and Exchange Commission.

For further information contact:

Investar Holding Corporation

Chris Hufft

Chief Accounting Officer

(225) 227-2215

Chris.Hufft@investarbank.com

INVESTAR HOLDING CORPORATION

CONSOLIDATED BALANCE SHEETS

(Amounts in thousands, except share data)