Background We sought to examine fracture settling and screw penetration after open reduction–internal fixation of 2-, 3-, and 4-part proximal humeral fractures and determine whether the use of calcium phosphate cement reduced these unwanted complications. Methods We performed a retrospective study of prospective data. Inclusion criteria included patient age of 18 years or older and an acute traumatic fracture of the proximal humerus that was treated with open reduction–internal fixation with a locked plate. Metaphyseal defects were treated with 1 of 3 strategies: no augmentation, augmentation with cancellous chips, or augmentation with calcium phosphate cement. Various radiographic measurements were made at each follow-up visit to assess for humeral head settling or collapse. Overall, 92 patients (81%) met the inclusion criteria and form the basis of this study. Augmentation type included 29 patients (32%) with cancellous chips, 27 (29%) with calcium phosphate cement, and 36 (39%) with no augmentation. Results There were no statistical differences among the groups with respect to patient age, sex, and fracture type. At the 3, 6, and 12-month follow-up visits, there was less humeral head settling with calcium phosphate cement compared with repair with no augmentation or with cancellous chips. Findings of joint penetration were significant among patients treated with plates and screws alone versus those augmented with calcium phosphate (P = .02) and for those augmented with cancellous chips versus those augmented with calcium phosphate (P = .009). Conclusion Augmentation with calcium phosphate cement in the treatment of proximal humeral fractures with locked plates decreased fracture settling and significantly decreased intra-articular screw penetration.