Hand gestures have a close link with speech and with social perception and persuasion processes, however to date no one has experimentally investigated the role of hand gestures alone in persuasive speech. An experiment with undergraduates was conducted using 5 video-messages in which only hand gestures of the speaker were manipulated along five types. ANOVAs reveal effect of gesture type on receivers’ evaluation of message persuasiveness, speaker communication style effectiveness, and speaker's composure and competence. A control study (Experiment 2) confirms that these effects are due to visible gestures. Speech accompanying gestures appear to play a causal role in social perception.