Modern-day organizations often utilize team-based designs, and employees increasingly work simultaneously on multiple teams. These working arrangements have been referred to as multiple team memberships, and despite their prevalence, they have been the subject of relatively little research. Applying social identity theory as a theoretical lens, we advance a multilevel conceptual model that suggests both individual and team characteristics predict individuals’ performance and satisfaction per membership, as mediated by their team identification per membership. We employed cross-classified effects analyses to model the combined influences of two sets of higher-level factors corresponding to individual (N = 96) and team characteristics (N = 82) on lower-level individual members’ team identification and related outcomes per team membership (N = 320). Analyses of multisource temporally lagged data from software development professionals, who were assigned to work in multiple teams, yielded support for the combined influences of individual and team-level factors on individuals’ identification with, and ultimately performance in and satisfaction with, their multiple team memberships. Implications for theory and practice are discussed.