This study aims to elucidate how industrial designers and engineering designers collaborate, and how such an alliance reflects in the design process. We conducted in-depth interviews about actual product design projects with 34 industrial and engineering designers from six consumer product manufacturers. We firstly identified individual design processes from the interview data. Secondly, we then compared and merged the design processes into collaborative processes using a mosaic method. We finally simplified the collaborative processes to create representative process models. As a result, we discovered four types of typical collaborative product design processes and their characteristics Type 1: ID-led Concept-driven Process, Type 2: ID-led Combined Outside-inside Process, Type 3: ED-led Inside-first Process, and Type 4: ID&ED Synergetic Process. (C) 2016 Elsevier Ltd. All rights reserved