The paper proposes a model for assessing the maturity of new service development (NSD) processes in manufacturing companies that offer product-services. The model adopts a five-stage scale on which key elements are evaluated according to the following dimensions: (1) the approach used to manage processes and projects (2) the use of specific resources, skills and tools (3) the involvement of customers, suppliers and other stakeholders and (4) the adoption of performance management systems. An empirical application of the model was carried out based on an inter-company workshop and in-depth interviews. Such a model allows not only to describe the maturity of NSD processes of a company but also to identify the main gaps and to prioritize improvement actions.