There is growing evidence linking teamwork practices to performance outcomes. However, critics have raised concerns that such outcomes are achieved at the expense of increased job demands and stress among workers. Using large data from a representative sample of British workplaces (N = 4,311 workers in 664 workplaces), this study explores the pattern of relationships between teamwork practices, organisational performance, and employee well‐being. The study draws on a mutual gains model linking teamwork practices to organisational performance via affective commitment, and a conflicting outcomes model associated with high job demands and job‐related anxiety. The study also examines an interactive outcomes model that integrates the mutual gains and conflicting outcomes models. The study reports evidence that the performance gains of teamwork practices may actually come at the cost of increased job demands and job‐related anxiety. Nevertheless, these adverse outcomes tend to weaken at higher levels of affective commitment.