Services constitute strategic components of firms’ value proposition, specifically for manufacturing firms currently called to servitize their products to develop product-service systems. In order to develop new services, they need to acquire, assimilate, transform and exploit external knowledge, thereby partnering with external stakeholders, a strategy labelled open service innovation. Yet research on innovation management in general and open innovation in particular has mostly focused on product innovation, leaving this area of research scantly understood. This is particularly true for manufacturing firms involving a family in the business, namely family manufacturing firms, acknowledged for adopting distinctive innovation behavior. With the intention of addressing this gap, we conceptually investigate open service innovation in family manufacturing firms by embracing a relational perspective. In so doing, we identify drivers and contingencies of family manufacturing firms’ innovation behavior that might trap them in their own net(work) and suggest managerial solutions to escape from such trap.