This study investigates the effects of the use of social media in inbound open innovation on capabilities for absorptive capacity of companies. Seven explorative case studies were conducted in an R&D and business context of two large global high‐tech companies. The results suggest that if the necessary conditions are met, social media usage increases the transparent, moderational and multi‐directional interactions that in turn influence four capabilities for absorptive capacity: connectedness, socialization tactics, cross‐functionality and receptivity, a hitherto overlooked capability. Hence, we observe that social media are boundary‐spanning tools that can be used to build and increase companies' absorptive capacity.