Ever increasing product complexity is an obstacle to effective product development. This paper introduces an agent-based model to study the impact of complexity during product design. Product was modeled as a set of functions that require knowledge, design effort and integration, and designers were modeled as agents who applied knowledge to function development tasks and communicated with each other. Simulation experiments were conducted to study the impact of variables, such as: designers’ knowledge level, designers’ experience, coordination efficiency and organizational structure under different levels of product complexity. The results suggest that an increase in complexity increases effort and span time exponentially. Thus, for the development of complex products, more effective coordination mechanisms should be applied when a project has very high levels of complexity and innovation. Having more knowledgeable and experienced designers also helps to lessen design effort and shorten span time. No assertion could be made as to whether a team or matrix organizational structure was superior.