Abstract This study investigates the differential effects of monolingual (L1 or L2) and bilingual (L1+L2) subtitles on students’ receptive vocabulary acquisition. In light of the widespread use of bilingual subtitles in videos in language classrooms with limited supportive literature available, this study aims at examining the pedagogical effects of bilingual subtitles on receptive vocabulary acquisition in the L2 classroom. A seven-week quasi-experimental study was conducted among four year-3 English-major classes in a Chinese university: three treatment groups and one control group. Adopting a counterbalanced design, students in the treatment classes were exposed to three types of subtitles within three videos. They were then tested on recall and recognition of the vocabulary target items encountered in the videos. The results demonstrate a significant advantage for bilingual subtitling in videos in terms of students’ vocabulary recognition and recall at post-test, and this advantage is maintained at the delayed post-test. Implications of the study are discussed in the context of current pedagogical practices such as a wider L1 use in the L2 classrooms.