This study examined the influence of small-group discussions on early adolescents' social reasoning development. A total of 147 fifth-grade students (79 males and 68 females) from six classrooms in a public school in Taiwan participated in a pre-post control quasi-experimental study. Classrooms of students were assigned to either a 5-week collaborative social reasoning (CSR) condition or an active-control read-aloud (RA) condition. All students completed a social reasoning essay before and after the intervention. Students in the CSR condition generated more social knowledge, considered more possible solutions to the complex social-moral issue, and reflected on more cognitive perspectives of the story characters. Students in the RA condition generated more shallow interpretations and were more attuned to affective perspectives of the story characters. CSR students' social reasoning tended to be more coherent, complex, and involve knowledge coordination. These findings lend support to the claim that CSR discussion is a productive vehicle for enhancing students' social reasoning.