Television can be considered a rich, helpful, and valuable source to expose L2 learners to huge amounts of comprehensible input so that they can improve their L2 knowledge and, in particular, their L2 vocabulary knowledge. This study aimed to discover how effective sustainable and extensive TV viewing can be in L2 vocabulary learning, considering the language of the on-screen text (L1 or L2) and instruction type (preteaching L2 items or not). Eighty L2 learners (58 female and 22 male), who had an intermediate English proficiency and were divided into four groups, participated in the intervention over an academic term in a language institute. Participants viewed 14 episodes of a TV series under four experimental conditions: (1) captions and preteaching, (2) captions without preteaching, (3) subtitles and preteaching, and (4) subtitles without preteaching. A pre/posttest design to examine the gains regarding both L2 vocabulary meaning and form was adopted. Results suggested that extensive exposure to TV series positively affected the participants’ L2 vocabulary learning, both in terms of meaning and form. Participants exposed to L2 captions outperformed those who had received L1 subtitles, concerning both L2 vocabulary meaning and form. Finally, the analyses showed that, overall, the groups that had undergone preteaching performed better, regardless of the language of the on-screen texts.
