〔Abstract〕 Objective To compare pain relief, functional improvement, and complications after an intratendinous leukocyte–poor platelet-rich-plasma (Lp-PRP) injection versus a subacromial corticosteroid injection for partial supraspinatus tears. Methods 60 patients with partial supraspinatus tears admitted to the First Affiliated Hospital of Shenzhen University from April 2020 to March 2022 were randomly assigned to Lp-PRP group and corticosteroid group, with 30 cases in each group, Pain relief and functional improvement were assessed using the visual analog scale (VAS) and the University of California at Los Angeles shoulder rating scale (UCLA), respectively. Treatment efficacy and complications were recorded, and the 2 groups were compared at 1-, 6- and 12-month follow-up. Results The VAS scores of the two groups after treatment were significantly lower than those before treatment, and the VAS scores of the observation group after treatment showed a continuous downward trend. The UCLA scores of both groups have increased compared to before treatment, and the differences were statistically significant (P < 0.05). At 6- and 12-months after treatment, the VAS scores of the observation group were lower than those of the control group, and the UCLA scores were higher than those of the control group, and the differences were statistically significant (P < 0.05). There were no complications during treatment in either group. Conclusion In patients with partial supraspinatus tears, a corticosteroid or Lp-PRP injection resulted in a similar reduction in pain and improvement in function after 1 month. However, at 6- and 12-month follow-up, Lp-PRP was superior to corticosteroids in clinical outcome improvement.