Wind turbines are known to cause bat fatalities worldwide. Ultrasonic acoustic deterrents are a potential solution to reduce impacts on bats, but few experimental field studies have been conducted at utility scale wind energy facilities. Our objective was to assess effectiveness of a recently developed deterrent for reducing bat fatalities at wind turbines in southern Texas, USA. We quantified fatalities at control (deterrents off) and treatment (deterrents on) wind turbines from 31 July through 30 October in 2017 and 2018, and assessed deterrent effectiveness using generalized linear mixed models. Our results indicate deterrents significantly reduced bat fatalities for Lasiurus cinereus and Tadarida brasiliensis by 78% and 54%, respectively. We observed no significant reduction in fatalities for other species in the genus Lasiurius. Thus, deterrents represent a potential impact reduction strategy for some bat species, but research is still warranted to improve species-specific effectiveness.