Many manufacturers are in the process of evolving from mass production to mass customization to cope with the increasing diversity of customer requirements. This induces an increasing complexity resulting from the high variety offered to customers. This problem is heightened by integrating product and service within the same offering. Modularity is considered as a driver for reducing complexity while increasing offered variety of products and services. This paper addresses the question of how to modularize products and/or services considering different criteria from the designers and domain experts. To this end, a Design Structure Matrix (DSM) based method is introduced. The method relies on a set of modularization criteria and on clustering to form product and/or service modules. The applicability of the method is illustrated through a test case in the manufacturing sector.