This paper investigates a multidisciplinary framework that simulates design decisions in a complex team-based product development in which engineers simultaneously work on a team project and individual projects. The proposed framework integrates collaborative design with (1) equilibrium analysis, (2) uncertainty modeling based on behavioral game-theory results, and (3) noncooperative decision making using decision analysis. In the proposed framework, noncooperative decision making is used to simulate engineers’ decisions about team-project commitment and to analyze potential free riding. Collaborative design is used to model design outcomes when engineers commit to the team project. Equilibrium analysis and behavioral game-theory results are used to infer uncertainty about other engineers’ decisions. Decision analysis is used to calculate expected values of decision alternatives. The proposed framework and the design decision making model are illustrated using a pressure vessel design as a team project conducted by two engineers: a design engineer and a materials engineer.