This paper investigates how newly hired workers learn on the job and the extent to which this learning is affected by their co-workers’ tenure. We estimate tenure-performance profiles using weekly panel data on individual workers’ performance. The results show a performance increase of 64% in the first year of the employment. We show that, during the first three months, workers placed in teams with more experienced peers have significantly steeper tenure-performance profiles than those employed in teams with less experienced peers. Our results suggest that placing new workers in more experienced teams reduces the time new hires need to become equally productive as an experienced worker by 36%, compared to being placed in less experienced teams.