Guided by self-determination theory, we conducted a live lecture experiment in two 50-min college courses to manipulate autonomy-supportive instruction (i.e., the amount of choices and rationales offered to students). Participants were 201 undergraduate students who either attended a lecture where the instructor gave students choices over the material learned and emphasized the relevance of the lecture and activities (experimental condition), or attended another lecture where the instructor taught without student choices and refrained from mentioning the relevance (control condition). During the lectures, students completed learning activities, and after the lectures, students reported on their intrinsic motivation toward their learning activities, along with their sustained attention to the lecture, and their likelihood of participating and communicating negative word-of-mouth. Results revealed that autonomy-supportive instruction caused students to (a) become more intrinsically motivated, which in turn, caused them to (b) put more effort into completing a learning packet, (c) sustain their attention, and report they would (d) participate in future classes with that instructor, and (e) refrain from spreading negative comments.