This study applies faultline, diversity and network perspectives to understand the functioning of multicultural teams (MCTs). Specifically, this study explores the effects of faultlines on the process and performance of multicultural teams while at the same time taking into account team members’ actual network ties. I propose that different types of faultlines influence team process and performance differently. I particularly examine faultlines based on both cultural values and surface-level attributes (e.g., demographics), as well as faultlines based on both cultural values and deep-level attributes (e.g., differences in beliefs and attitudes). I also examine how network ties that span cultural subgroups created by faultlines influence these same process and outcome variables. A cross-sectional and longitudinal investigation of more than 100 research teams at a major research university provides evidence for a complex pattern of the impact of faultlines and network ties. The results demonstrate that faultlines alone do not contribute to team processes or performance. Instead, their effects depend on the social interaction patterns that cut across them. Specifically, team performance improved when friendship ties cut across subgroups formed by cultural faultlines, but relationship conflict increased and team performance decreased when animosity ties cut across these subgroups. Overall, the results highlighted the importance of taking into account team members’ actual network patterns while studying the effects of team composition on team process and performance. These results generate many fruitful implications for theory and practice. Directions for future research are suggested.