Background and aim De Quervain's tenosynovitis (DQST) is a prevalent condition involving tendon inflammation in the wrist. This study compares the clinical and functional outcomes between patients receiving platelet-rich plasma (PRP) injections and those receiving corticosteroid injections for DQST. Methods A retrospective study conducted at Sri Devaraj Urs Academy of Higher Education and Research, Kolar, India, included 58 patients with DQST, divided into Group A (PRP injection) and Group B (corticosteroid injection). Assessments were conducted using the Visual Analogue Scale (VAS), the Disabilities of the Arm, Shoulder, and Hand (DASH) score, and the Modified Mayo Wrist Score (MMWS) at baseline, one month, three months, and six months. Statistical analyses were performed using IBM SPSS Statistics for Windows, Version 22.0 (Released 2013; IBM Corp., Armonk, NY, USA), with significance set at p < 0.05. Results Both treatment groups demonstrated a reduction in VAS scores over time. Significant improvements were observed at one month (p = 0.007) and six months (p = 0.004) post-injection. Baseline (p = 0.336) and three-month (p = 0.829) VAS scores showed no significant differences. Similarly, DASH scores were not significantly different at any measured time points: baseline (p = 0.331), one month (p = 0.592), three months (p = 0.707), and six months (p = 0.314). MMWS scores also showed no significant differences at baseline (p = 0.123), one month (p = 0.101), three months (p = 0.422), and six months (p = 0.956). Independent sample t-tests highlighted significant VAS score improvements at one month (t = 2.813, p = 0.007) and six months (t = -3.009, p = 0.004), but DASH and MMWS scores showed no significant differences at any time points. Chi-square tests indicated no significant associations between the groups at one-month, three-month, and six-month follow-ups. Conclusion Both PRP and corticosteroid injections effectively alleviate pain in DQST patients, as evidenced by significant VAS score improvements. However, functional outcomes measured by DASH and MMWS scores did not significantly differ between the treatments. These results suggest that while both treatments are effective for pain management, their short-term impact on functional improvement may be similar. To investigate long-term functional results, more research with bigger sample sizes and longer follow-up periods is required.