The efficient scheduling of the new product development (NPD) projects is important to reduce the required development time, and to offer the new product faster. Activity overlapping is commonly regarded as the most promising strategy to reduce product development times. However, overlapping must be well-planned by weighting the gain from the activity overlapping against the additional time for rework. The objective of this research was to develop a resource constrained scheduling methodology for NPD projects considering overlapping of activity couples. A particle swarm optimization based approach is used to schedule NPD projects that include overlapping process. The proposed PSO method is developed into a user friendly system so that the practitioners can utilize it. A real-life example of a product development project taken from the literature is used to show the efficiency of the software. (C) 2015 Elsevier Ltd. All rights reserved.