BACKGROUND: Previous studies have demonstrated that psychosocial factors and comorbid depression are associated with worse preoperative baseline measures, clinical outcomes, and recovery in patients undergoing shoulder surgery. It is unknown whether this potential link would differ between those with traumatic vs. atraumatic shoulder instability, as symptoms may persist longer in atraumatic instability prior to surgical intervention. The purpose of this study was to determine if psychosocial factors and/or comorbid depression more heavily influence preoperative symptoms for patients with traumatic vs. atraumatic shoulder instability. METHODS: Prospective baseline data from 1552 patients in the Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Instability cohort were analyzed based on mechanism of injury while controlling for age, sex, and direction of instability. Multivariable linear regressions were performed to determine whether psychological factors (RAND 36 Mental Component Score [MCS], depression diagnosis, Personality Assessment Screener-22) were predictive of preoperative American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) and Western Ontario Shoulder Instability Index (WOSI) scores in the atraumatic group. The same model was repeated for the traumatic instability group, and the model fit was compared between groups, with P < .05 considered statistically significant. RESULTS: Female sex and lower MCS were significantly associated with worse preoperative ASES and WOSI scores for the group with atraumatic instability (ASES R2 = 0.15, P < .001; WOSI R2 = 0.17, P < .001). The same model performed significantly worse (P < .05) for both ASES and WOSI scores in the group with traumatic instability (ASES R2 = 0.07, WOSI R2 = 0.08). CONCLUSIONS: Worse preoperative psychosocial factors were found to be more strongly associated with shoulder-related pain and function for patients with atraumatic instability. Across multiple orthopedic conditions, depression and emotional well-being have been associated with worse preoperative symptoms and inferior postoperative patient-reported outcomes. Despite the stronger and significant association in atraumatic patients, worse psychosocial factors did not have as large an impact as has been seen in other, more chronic conditions such as osteoarthritis or rotator cuff tears. In addition to medically optimizing patients prior to surgery, the current findings identify a subset of shoulder instability patients that may benefit from a behavioral health intervention either prior to surgery or early in the postoperative period to potentially improve postoperative outcomes.