Objective To compare the effectiveness of simultaneous and delayed repair of combined full-thickness rotator cuff rupture in proximal humerus fracture. Methods Between January 2015 and January 2017, 44 patients with proximal humerus fractures complicated with full-thickness rotator cuff injuries were included. Twenty-four patients underwent open reduction and internal fixation (ORIF) and rotator cuff repair simultaneously (simultaneous operation group), and 20 patients underwent delayed arthroscopic rotator cuff repair more than 90 days after ORIF (delayed operation group). There was no significant difference in gender, age, cause of injury, and side of injury between the two groups (P>0.05). The fracture healing was observed by X-ray films. The shoulder function was assessed at 3, 6, and 12 months after operation by using the University of California at Los Angeles (UCLA) score. Results All incisions healed by first intention. All patients were followed up 12-24 months (mean, 17 months). Fractures all healed at 3 months after operation in simultaneous operation group. According to UCLA score, the patients had achieved significantly better outcomes in function, active forward flexion, strength of forward flexion, and subjective satisfaction in simultaneous operation group than in delayed operation group at 3, 6, and 12 months after operation (P<0.05). However, there was no significant difference in pain between the two groups (P>0.05). Conclusion For patients with proximal humerus fracture complicated with full-thickness rotator cuff rupture, performing ORIF and simultaneous repair of rotator cuff can improve shoulder function and achieve better effectiveness when compared with delayed repair of rotator cuff.