This study investigated how interaction with peers influenced the ways students managed uncertainty during collaborative problem solving in a 5th-grade class. The analysis focused on peer responses to individuals' attempts to manage uncertainty they experienced while engaged in collaborative efforts to design, build, and program robots and achieve assignment objectives. Patterns of peer response were established through discourse analysis of work sessions for 5 teams engaged in 2 collaborative projects. Three socially supportive peer responses and 2 unsupportive peer responses were identified. Peer interaction was influential because students relied on supportive social response to enact most of their uncertainty management strategies. This study provides a useful theoretical contribution to understanding the roles of peer interaction in collaborative problem solving. Conceptualizing collaborative problem solving as a process of negotiating uncertainties can help instructional designers shape tasks and relational contexts to facilitate learning.