This article focuses on the phenomenon of interfirm labor mobility as a potential channel for knowledge transfer. Using data from the Danish employer-employee register covering the period 1995-2005, we investigate how knowledge carriers-technicians and highly educated workers recruited from a donor firm-contribute to knowledge diffusion and enhanced productivity in the hiring (recipient) firm. Structural estimation of the hiring firms' production functions shows that the impact of the recruitment of knowledge carriers on a firm's value added is an increase of 1%-2%. Several robustness checks confirm this finding.