Open innovation (OI) has been appointed as a key factor to promote innovative performance, but some research gaps remain especially when it comes to SMEs in developing countries. This article deals with (1) the effect of formalization of innovation strategy on OI activities in SMEs, (2) the impact of OI activities on SMEs’ innovative performance, and (3) the moderating role played by control on the relationship between inbound and outbound activities and the innovative performance. OI encompasses a range of innovative methods and procedures in firms to stimulate internal innovation and widen the external use of innovation (inbound and outbound). In this work, an empirical study is carried out on 543 Ecuadorian SMEs. The results show that the formalization of the innovation strategy promotes OI activities, both inbound and outbound. While outbound activities carried out by SMEs enhance innovative performance, this positive effect is only identified for inbound open innovation activities when control exists and increases, acting this variable as a moderating factor. These results have important implications both for the management of companies and the development of public policies aimed at promoting OI in SMEs in developing countries. This research contributes to the literature as it deals with a developing country context and considers a wide range of OI activities.