Background: Needle aspiration of calcific deposits (NACD) is a frequently used treatment for rotator cuff calcific tendinitis (RCCT). However, a substantial number of patients experience recurrent or persisting shoulder symptoms after NACD. Purpose: To compare the effects of adjuvant application of platelet-rich plasma (PRP) after NACD (NACP+PRP) with those of conventional NACD with corticosteroids (NACD+corticosteroids) on pain, shoulder function, and quality of life (QoL). Study Design: Randomized controlled trial; Level of evidence, 1. Methods: In a single-center, double-blinded, randomized controlled trial, 80 adults with symptomatic RCCT were randomly allocated to receive NACD+corticosteroids or NACD+PRP. Pain, shoulder function, and QoL were assessed at baseline; 6 weeks; and 3, 6, 12, and 24 months after treatment using a numeric rating scale for pain (NRS); the Constant-Murley score (CMS); the Disabilities of the Arm, Shoulder and Hand questionnaire (DASH); the Oxford Shoulder Score (OSS); and the EuroQol 5-dimension scale (EQ-5D). Additionally, resorption of calcific deposits and the integrity of rotator cuff tendons were assessed by using standard radiographs and ultrasound examination, respectively. The results were analyzed using noninferiority analysis for NRS scores and a mixed model for repeated measures. Results: Eighty patients were included (48 female; mean age, 49 ± 6 years; 41 patients in the NACD+PRP group). Both groups showed improvement of clinical scores at the 2-year follow-up ( P < .001 for all clinical scores). NACD+PRP was found to be noninferior to NACD+corticosteroids with regard to the mean decrease of NRS scores (4.34 vs 3.56; P = .003). Mixed-model analysis showed a significant difference in favor of NACD+PRP (CMS, P < .001; DASH, P = .002; OSS, P = .010; EQ-5D, P < .001). However, clinically relevant differences in favor of NACD+PRP were only seen at the 6-month follow-up for NRS and CMS scores, whereas at the 6-week follow-up a clinically relevant difference in favor of NACD+corticosteroids was found for all clinical scores except for the NRS. Full resorption of calcific deposits was present in 84% of the NACD+PRP group compared with 66% in the NACD+corticosteroids group ( P = .081). In the NACD+PRP group, 10 (24%) patients required a second NACD procedure compared with 19 (49%) patients in the NACD+corticosteroids group ( P = .036). Six complications, of which 5 were frozen shoulders, occurred in the NACD+PRP group compared with 1 complication in the NACD+corticosteroids group ( P = .11). Conclusion: NACD+PRP resulted in worse clinical scores at the 6-week follow-up but better clinical scores at the 6-month follow-up compared with NACD+corticosteroids. At the 1- and 2-year follow-ups, the results were comparable between groups. Furthermore, PRP seemed to reduce the need for additional treatments but was associated with more complications. In conclusion, NACD+corticosteroids had a favorable early effect on pain and function combined with low comorbidity. Thus, it remains the treatment of choice for patients with RCCT. Registration: NCT02173743 (ClinicalTrials.gov identifier).