We used a randomized clinical trial to investigate the interaction of two patient personality characteristics (quality of object relations [QOR] and psychological mindedness [PM]) with two forms of time-limited, short-term group therapy (interpretive and supportive) for 139 psychiatric outpatients with complicated grief. Findings differed depending on the outcome variable (e.g., grief symptoms, general symptoms) and the statistical criterion (e.g., statistical significance, clinical significance, magnitude of effect). Patients in both therapies improved. For grief symptoms, a significant interaction effect was found for QOR. High-QOR patients improved more in interpretive therapy and low-QOR patients improved more in supportive therapy. A main effect was found for PM. High-PM patients improved more in both therapies. For general symptoms, clinical significance favored interpretive therapy over supportive therapy. Clinical implications concerning patient-treatment matching are discussed.