Service innovation has become increasingly important for the growth of developed and developing countries. Despite an extensive body of literature on the role of joint innovation capabilities in improving a firm's innovativeness, the multivariate influences of operant resources and joint innovation capabilities, as well as the interplay among these in the prediction of service innovation have not been scrutinized in the context of B2B SMEs in a developing country. This study aims to fill this gap by testing a model that shows the relationships among complementarity of knowledge and capabilities as operant resources, joint innovation capabilities, and service innovation. We derive hypotheses about these relationships and test them using data from a sample of 302 respondents from 151 firms operating in the UAE. The results show that the relationships between complementarity of knowledge and joint innovation capabilities, and between joint innovation capabilities and service innovation, are significant and positive. They also show that the mediation effect of joint innovation capabilities on the relationship between complementarity of knowledge and service innovation is positive and full. This study also tests the moderating roles of competitive intensity and demand uncertainty in the relationship between joint innovative capabilities and service innovation and finds that their connection is stronger when competitive intensity is high. •Knowledge complementarity helps develop joint innovation capabilities.•However, complementarity of capabilities has no such effect.•Joint innovation capabilities can create superior service innovation.•Competition enhances the effect of joint innovation capabilities on service innovation.•Joint innovation capability in emergent markets rely more on knowledge complementarity.