This study investigates incidental vocabulary learning through captioned or subtitled videos and examines whether and how different learner- (prior vocabulary knowledge) and word-related factors (i.e., frequency of occurrence, cognateness, and imagery) influence learning gains from watching videos. Low-intermediate Dutch-speaking learners of French (N=86) took part in a four week intervention program. They were assigned to a subtitles group, a captions group, or a control group (who only took the tests). Vocabulary learning was measured by means of form and meaning recognition, as well as meaning recall tests. Results revealed that participants learned approximately 15% of the vocabulary they could have learned. Both treatment groups outperformed the control group in the meaning recognition test, but only the captions group outperformed the control group in the meaning recall test. Learning gains were mediated by cognateness with significantly higher odds to recall and recognize a cognate on the posttest than a noncognate. Frequency of occurrence and prior vocabulary knowledge had a positive effect on L2 learners' ability to recall and recognize the meaning of the target words. A positive relationship was also found between target words that were visually represented in the video and learners' meaning recall scores for those words.