This study delineates cooperation and competition and their interaction effects on system design quality through prototype design processes. The data is collected using a questionnaire from 322 respondents who comprised 161 information system development teams in Taiwan. Comprehensiveness, constructive debate and integrative solutions are significantly associated with system design quality. Indeed, when both cooperation and competition are high, team members are more deeply involved in comprehensiveness, constructive debate and integrative solutions. The coexistence of cooperation and competition is significantly related to comprehensiveness and constructive debate. Under low cooperation, team members who receive competition will reach higher involvement in comprehensiveness and constructive debate because they engage in practices to gain competitive advantages. The implications of these findings are discussed along with future directions for academic research and managerial practice in information system development.