This study examined gains undergraduate students made in their communication and collaboration skills when they served as peer teachers, i.e., laboratory instructors (LIs), for a General Psychology laboratory. Self-ratings of communication and collaboration skills were completed before and after teaching the laboratory. When compared to before the teaching experience, the students rated their skills significantly higher in written expression, oral expression, and participation skills. They also rated themselves significantly higher in written comprehension and expression skills than did a comparison group of non-LIs. Results from interviews also revealed beliefs that their communication and collaboration skills had substantially increased.