Lactobacillus wasatchensis is a slow growing, non-starter lactic acid bacterium (NSLAB) that causes late gas defect in aging cheese and results in significant economic losses to producers. During cheese aging, organic acids can be produced by other NSLAB cultures or purposefully added to cheese during manufacture. Organic acids are often used as food preservatives, can occur naturally in foods, and generally do not affect flavor or product quality. Selected organic acids, in their naturally occurring concentration ranges in Cheddar cheese, were investigated for their ability to inhibit Lb. wasatchensis WDC04. Five organic acids (lactic, formic, propionic, citric, and acetic) produced by NSLAB organisms were tested. They were each added at their minimum, median, and maximum concentrations, as found naturally in aged Cheddar cheese, to individual wells of a 48 well plate containing MRS broth with 1% ribose (MRS + R) inoculated with Lb. wasatchensis WDC04. Growth rates were determined on a Tecan Infinite 200 PRO spectrophotometer over 40 h. All tests were done in triplicate and a one-sided t-test used to determine significance (P < 0.05) between treatments and the control (no added organic acid). Initially, tests were done at pH 7.0 with several organic acids exhibiting some inhibition. Tests were then run at pH 5.0 to determine if the organic acids were more effective at a pH of aged cheese. Both formic and citric acid showed significant inhibition of Lb. wasatchensis WDC04, especially at pH 5.0. Formic acid was the most inhibitory of all 5 organic acids with the maximum concentration (100 mM) showing the greatest inhibition. Addition of citric acid at the minimum (12 mM) and median (13.5 mM) concentrations also produced inhibition. Use of selected organic acids at concentrations normally found in Cheddar cheese could be a potential antimicrobial measure to prevent or reduce late gas defect in aging cheese.