In the literature of Open Innovation (OI), some specific themes, such as elaboration of methods, strategies and systematized processes of implementation are still little discussed. In attempted to fill this research gap, this study aims to present a proposal for a framework for the implementation of OI in Small and Medium-sized Enterprises of Regional Innovation Systems (RIS). As such, it can support the theoretical development related to OI implementation methods and tools. The constructivist method was used in the development of the framework, which represents the Implementation Process of OI (IPOI), consisting of 5 stages: (i) diagnosis of RIS; (ii) diagnosis of the enterprise; (iii) preparation; (iv) implementation; and (v) monitoring and control. The unfolding of this process in stages and measurement systems allows us to understand the elements and Critical Success Factors (CSF) that interfere in the improvement of the capacity of innovation in SMEs inserted in RIS.