This research examines adult attachment and the investment model. Study 1 tests anxiety and avoidance predicting romantic relationship commitment, mediated by satisfaction, alternatives, and investments. Additional studies added outcomes of relationship maintenance (Study 2) and persistence (Study 3). In all 3 studies, satisfaction, alternatives, and investments mediated the associations between anxiety and avoidance and relationship commitment. A direct effect of avoidance on commitment remained. The investment model variables mediated the effect of anxiety and avoidance on accommodation and willingness to sacrifice (Study 2) and relationship persistence (Study 3). Direct effects remained for avoidance on accommodation and anxiety on persistence. The mediated model was supported for men and women, proximal and long‐distance relationships, and college student and community samples.