Arthroscopic rotator cuff repair typically leads to favourable clinical outcomes, but post-operative cuff re-tear remains a significant concern. This prospective randomized control trial investigated the potential healing effects of hyaluronic acid (HA) as an adjunct after cuff repair. Patients who had undergone arthroscopic rotator cuff repair from March 2019 to September 2020 were included in the study. Participants were randomly assigned to receive either HA injection or placebo post-operatively. Assessments were conducted at 2 weeks, 3 months, 6 months, and 12 months post-surgery. Outcomes measured included VAS pain scores, ASES, CONSTANT scores, range of motion, and strength. The integrity of cuff tendons was also evaluated through MRI, utilizing the Sugaya classification system. Administration of HA did not result in any significant differences in the VAS, ASES and CONSTANT scores, and manual strength, compared to placebo. No differences in complications and adverse events were seen between hyaluronic acid and placebo. More patients in the HA group attained full abduction, internal rotation, and external rotation by the 6th (53% vs. 40%) and 12th (73% vs. 60%) month compared to placebo. Both treatment groups consistently showed improvement on all outcome scores at final follow-up (p<0.001). MRI-assessed re-tear rates at final follow-up were lower in the HA arm (n=5, 14.4%) than placebo (n=8, 26.7%). This study suggests that immediate HA administration following arthroscopic rotator cuff repair may contribute to faster recovery of range of motion, and may reduce re-tear rates.