Background: Treatment options for calcific tendinitis (CT) of the shoulder remain controversial. A consensus for an operative indication for this condition is lacking. Purpose: To compare nonoperative versus operative treatment for shoulder CT and analyze factors affecting the prognosis after treatment. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 180 patients diagnosed with symptomatic CT between January 2017 and September 2021 were evaluated in this retrospective cohort study. There were 103 patients treated nonoperatively at our institution, which included the use of nonsteroidal anti-inflammatory drugs, acupuncture, steroid injections, extracorporeal shock wave therapy, and ultrasound-guided needle aspiration/percutaneous irrigation. However, 77 patients were treated with arthroscopic surgery after 6 months of failed nonoperative treatment. The visual analog scale (VAS) for pain, the Constant-Murley score, and imaging were used to assess and evaluate outcomes. Descriptive data, functional outcomes, and imaging findings were compared between the operative and nonoperative groups before and after propensity score matching. Additionally, prognostic factors including calcium deposit size, tendon infiltration by calcium deposits, involvement of single or multiple tendons, and occurrence of rotator cuff tears were analyzed by comparing the groups to determine their effect on treatment options and recovery. Results: Magnetic resonance imaging showed that the supraspinatus tendon (66.7%) was most commonly involved, followed by the infraspinatus (42.8%) and subscapularis (21.1%) tendons. Tendon infiltration by calcium deposits was observed in 84.4% of the patients, and rotator cuff tears occurred in 30.0% of the patients. After propensity score matching, there was no significant difference in changes in the Constant-Murley score (48.1 ± 25.4 vs 49.0 ± 22.8, respectively; P = .950) and VAS score (4.9 ± 2.3 vs 4.5 ± 1.9, respectively; P = .860) between the operative and nonoperative groups at the final follow-up. However, for patients with shoulder CT and without rotator cuff tears, there was a significant difference in changes in the Constant-Murley score (52.93 ± 25.18 vs 42.13 ± 22.35, respectively; P = .012) and VAS score (5.21 ± 2.06 vs 3.81 ± 1.98, respectively; P < .001) between the operative and nonoperative groups, but the recovery time in the operative group was longer than that in the nonoperative group (86.92 ± 138.56 vs 30.42 ± 54.97 days, respectively; P = .016). The results also showed that calcium deposit size, involvement of multiple tendons, and tendon infiltration by calcium deposits did not affect the recovery time after treatment. The survival analysis showed that rotator cuff tears affected the complete recovery of shoulder function. Conclusion: This study demonstrated no significant difference between nonoperative and operative treatment for patients with shoulder CT, on the whole. However, for patients with shoulder CT and without rotator cuff tears, the effect of operative treatment was better than that of nonoperative treatment; yet, operative treatment was shown to prolong the recovery time. Calcium deposit size, tendon infiltration by calcium deposits, and involvement of multiple tendons did not correlate with recovery time or the recovery of function. A rotator cuff tear was the only factor affecting the complete recovery of shoulder function.