The ability to infer psychological meaning in behaviour—referred to as psychological mindedness—has been posited as a patient characteristic that contributes to the therapy process and consequently to therapeutic success. The present study was developed to examine the relationship between patients' psychological mindedness and improvement in patients' personal treatment goals in interpretive and supportive group therapies for complicated grief, along with patients' importance to group process. The study was conducted with a clinical sample of 109 patients (79% female; average 45 years old) receiving treatment for complicated grief. Patients provided severity of distress ratings for individual target objectives at pretreatment and posttreatment. Psychological mindedness was assessed prior to treatment using the video‐based, interviewer‐rated Psychological Mindedness Assessment Procedure. Patients' importance to the therapy process was rated by therapists and other patients in interpretive and supportive group therapy for complicated grief. Conditional process modelling tested whether psychological mindedness would contribute to patients' goal achievement through patients' importance to group process, moderated by type of therapy. A significant, conditional indirect effect was observed for psychological mindedness as a predictor of improvement in individual target objectives, through patients' importance to group process as rated by therapists, specifically in interpretive therapy. The findings indicate that patients' psychological mindedness significantly contributes to their achievement of individual goals through their contributions to group process in interpretive group therapy. Further research is needed to understand the facilitation of individual goal achievement in supportive therapy.