Despite steady investment in English language education made by developing countries over the past few decades, results continue to be constrained by lack of high-quality instructors and language learning resources. Thus, using technology in language instruction has increasingly been recognized as a potential approach for addressing these constraints. This study uses administrative data from a large public university in Mexico to examine the impact of a technology-enhanced blended program on students' English course grades and course completion rates. Specifically, we focus on a campus-wide policy change in all compulsory English language courses that replaces half of the traditional face-to-face class time with an interactive online learning environment developed by a leading technology-mediated English language learning and assessment provider. Our results suggest that, compared to traditional face-to-face instruction, blended learning had a significant, positive impact on students' course grades and course completion rates. In addition, the enrollment-teacher ratio increased after replacing half of the face-to-face instructional time with online learning, suggesting that blended learning environments hold promise for providing high-quality and cost-effective language instruction.