Video games are potential sources of second language input; however, the medium's fundamental characteristic, interactivity, has not been thoroughly examined in terms of its effect on learning outcomes. This experimental study investigated to what degree, if at all, video game interactivity would help or hinder the noticing and recall of second language vocabulary. Eighty randomly-selected Japanese university undergraduates were paired based on similar English language and game proficiencies. One subject played an English-language music video game for 20 minutes while the paired subject watched the game simultaneously on another monitor. Following gameplay, a vocabulary recall test, a cognitive load measure, an experience questionnaire, and a two-week delayed vocabulary recall test were administered. Results were analyzed using paired samples t-tests and various analyses of variance. Both the players and the watchers of the video game recalled vocabulary from the game, but the players recalled significantly less vocabulary than the watchers. This seems to be a result of the extraneous cognitive load induced by the interactivity of the game; the players perceived the game and its language to be significantly more difficult than the watchers did. Players also reported difficulty simultaneously attending to gameplay and vocabulary. Both players and watchers forgot significant amounts of vocabulary over the course of the study. We relate these findings to theories and studies of vocabulary acquisition and video game-based language learning, and then suggest implications for language teaching and learning with interactive multimedia. (Contains 2 figures and 2 tables.)