© 2017 The Japanese Orthopaedic Association Background The objective of the study was to determine the normalization curve of the serum C-reactive protein (CRP) in elective shoulder arthroplasty. Methods A prospective study including 58 consecutive patients who had undergone elective shoulder arthroplasty. Forty-one patients had received a Reverse Shoulder Arthroplasty, 13 a Total Shoulder Arthroplasty and 4 a Hemiarthroplasty. Based on a pilot study, blood samples to determine CRP values were obtained at baseline (1 h before surgery), on the 1st, 2nd, 6th, 8th and 14th postoperative days. All the patients included presented no postoperative complications during inpatient stay or any re-admission during the three months after surgery. Results Mean CRP values showed a rapid increase on the 1st postoperative day (7-fold higher than the baseline in cuff tear arthropathy, 11-fold higher in primary osteoarthritis, 1-fold higher in acute fracture) and reached a peak on the 2nd postoperative day (14-fold higher than the baseline in cuff tear arthropathy, 24-fold higher in primary osteoarthritis and 2-fold higher in acute fracture). After the 2nd postoperative day CRP values began to slowly decrease reaching the normal range in the 14th postoperative day. Conclusions Serum CRP levels after elective shoulder arthroplasty rapidly increase to reach a maximum peak after the 2nd surgery day and then slowly decrease to return to normality on the 14th day. Knowing the normalization curve of CRP can be a helpful tool to help in the diagnosis of acute infections in elective shoulder arthroplasty.