Conflict occurrence during information systems (IS) development/implementation is an unavoidable phenomenon. Conflict strains interactions and trust, leads to further conflict, and has a negative effect on system implementation success. Therefore, resolving conflict that arises during the IS implementation process has been a crucial issue for decades. Unfortunately, the existing empirical evidences were not consistent with this conventional wisdom and lacking of a theoretical explanation. We argue that the integrative conflict management is an effective mechanism for conflict resolution under the multi-project system development context. We construct a model using controversy conflict theory in order to explain the effect of conflict resolution on IT projects implementation effectiveness. We test the model using data from 183 large-scale IT implementation projects. Our model and findings support our theory that integrative conflict management supports effective conflict resolution and program outcomes.