This paper presents a structured Project Risk Interactions Management (PRIM) process designed to make risk response planning decisions taking into account the complex interactions that potentially exist between project risks. Projects are facing tight constraints, uncertainty and change. Moreover, they are dealing with higher stakes and an ever-growing complexity, which implies that they are more than ever exposed to risks, and that these risks are strongly interrelated. Existing classical methods have some limitations for modeling and managing the project complexity, mainly the interactions that may exist between project risks. We propose to include the identification, assessment and analysis of these interactions into the classical Project Risk Management (PRM) process. This analysis gives new insights for risk response planning decisions. The strategies are always mitigation, acceptance, transfer or avoidance, but the risks which are defined as the most critical ones may be slightly different. There may also be innovative decisions, like breaking propagation transitions between interrelated risks, instead of acting on the risk itself. This process assists the project manager making decisions regarding risk response planning by providing new insights about the potential phenomena involved by complexity, about the internal weaknesses to cope with this complexity, and about the potential effectiveness of proposed mitigation actions. An example of application is detailed to illustrate the validity and the implementation issue of the process.