Background: Alopecia areata (AA) is a chronic, immune-mediated, non-scarring hair-loss disorder arising from a collapse of follicular immune privilege. Intralesional corticosteroids and platelet-rich plasma (PRP) are both used for localized disease, but comparative long-term data remain limited. Objective: To compare the efficacy, safety and relapse rates of intralesional triamcinolone acetonide (TAC) and PRP in patients with patchy AA. Methods: In this prospective interventional study, 60 patients aged 18–50 years with scalp-limited AA were allocated by systematic randomization into two groups of 30. Group A received double-centrifugation PRP and Group B received TAC (5 mg/mL); injections were given at 4-week intervals for 12 weeks. Response was assessed using the Severity of Alopecia Tool (SALT) score at baseline, 4, 8 and 12 weeks, with adverse events and relapse monitored to 9 months. Data were analysed in SPSS v25.0 with p < 0.05 considered significant. Results: Both groups improved progressively, but TAC produced significantly faster early reduction in SALT scores at 4, 8 and 12 weeks (p = 0.03, 0.04 and 0.05). Excellent improvement (>75%) at 12 weeks was seen in 46.7% of TAC versus 33.3% of PRP patients. At 9 months, mean SALT scores were comparable (6.8 ± 4.1 vs 6.1 ± 3.5; p = 0.42). Skin atrophy (20%) and hypopigmentation (13.3%) occurred only in the TAC group, and relapse was lower with PRP (10% vs 26.7%). Shorter disease duration, fewer patches and lower baseline SALT predicted better response. Conclusion: TAC and PRP are both effective for patchy AA. TAC achieves faster early regrowth, whereas PRP offers comparable long-term efficacy with a superior safety profile and a lower relapse tendency, making it a useful steroid-sparing alternative.