This study extended research on gender differences in creative stories written by individuals to creative stories written in collaboration with a same- or an other-gender peer partner. Participants were 104 preadolescent sixth graders, mostly White and middle class. Same- and other-gender peer partners (18 girl, 16 boy, and 17 mixed-gender dyads) worked together for 4 weeks to write creative stories based on “mystery pictures.” Story ideas were coded into one of seven categories (i.e., overt aggression, verbal aggression, relational aggression, prosocial behavior, negative emotion, positive emotion, and neutral/other). Boy dyads' stories included a greater proportion of overtly aggressive story ideas and a lesser proportion of prosocial story ideas than did girl dyads' stories. Mixed-gender dyads' stories contained a greater proportion of prosocial ideas than did boy dyads' stories. Findings are discussed in light of a social-contextual approach to gender differences and similarities.