The adoption of Industry 4.0 technologies may represent an interesting opportunity for many SMEs, but the implementation of these technologies may be hindered by the lack of several resources. In this paper, we investigate how Open Innovation (OI) can help SMEs in the adoption of I4.0 technologies. Specifically, we show that both OI breadth and depth may be positively related to the adoption of these technologies. Besides, we highlight how the effect of OI depth is positively moderated by the technological intensity of the industry where the SME operates. Our results offer theoretical contribution to the literature on SMEs' I4.0 technologies' adoption, as well as that on OI. Finally, our findings can support both managers and policy makers in the implementation of I4.0 technologies.