Although English language learners (ELLs) have an increasing presence in postsecondary education, their unique needs are often unmet by institutions of higher education, partly resulting from their diversity--they vary in their educational backgrounds, English proficiency levels, career goals, and reasons for learning English. Many ELLs spend valuable time and money on remedial courses that do not meet their educational needs, which makes them less likely to persist in their coursework or enter a degree track. Technology-mediated English language instruction may be a solution to the pressing challenges that postsecondary institutions face in providing personalized instruction to ELLs, because it allows instruction to be tailored to an individual's English proficiency, academic needs, and professional interests. This study specifically tested the efficacy of one such educational technology--Voxy, a web- and mobile-based application--for improving ELLs' English language proficiency. The purpose of this quasi-experimental study was to understand whether access to Voxy's online platform as part of the regular coursework in a community college language laboratory improved ELLs' English language acquisition after one semester. The two primary research questions were these: (1) Does access to Voxy's web and mobile platforms increase ELLs' English language proficiency after one semester?; and (2) How is student use of the Voxy platform related to English language proficiency? After one semester of use: (1) Students with access to Voxy had larger English language gains than their peers in the comparison group; and (2) Platform usage was lower than recommended, but students consistently used Voxy outside of regular lab times. Findings provide promising evidence that Voxy can support English language learning in community college language labs.