Scholars have long been aware of the advantages of social capital to individual performance. It remains unclear whether these advantages reflect the effects of relationships in which people discuss only work-related issues, or whether they are attributable to the effects of multiplex relationships, in which people discuss work-related and non-work-related issues. To investigate this question, we conducted two studies using network analysis: a cross-sectional study of specialty bank employees and a longitudinal study of middle managers enrolled in an MBA course. Multiplex relationships consistently predicted performance advantages in both samples, whereas work-focused ties that excluded a social dimension did not. Furthermore, when individuals maintained too many multiplex relationships, performance returns diminished. These findings demonstrate that the network literature may benefit from greater specificity on relational content and more attention to the consequences of overlapping networks, in the form of multiplex ties.