Adolescents undergo critical developmental transformations that increase the salience of peer influence. Peer interactions (platonic and romantic) have been found to have both a positive and negative influence on adolescent attitudes and behaviors related to romantic relationships and sexual behavior. This study used qualitative methodology to explore how peers influence romantic and sexual behavior. Forty adolescents participated in individual semi-structured interviews. All interviews were audio recorded and transcribed, and analyzed using a modified grounded theory approach. The concept of peer influence on romantic relationships and sexual behavior emerged as a key theme. Youth described that platonic peers (friends) influenced their relationships and sexual behavior including pressuring friends into relationships, establishing relationships as currency for popularity and social status, and creating relationship norm and expectations. Romantic peers also motivated relationship and sexual behavior as youth described engaging in behavior to avoid hurting and successfully pleasing their partners. Future research should explore multiple types of peer influence in order to better inform interventions to improve the quality of adolescents' romantic and sexual relationships.