One hundred thirty-nine patients undergoing elective primary total hip arthroplasty were randomized to receive melatonin 5 mg nightly (n=75) or placebo (n=64) for 14 days after surgery. The primary outcome of interest was sleep disturbance, assessed using PROMIS-SD scores on postoperative day 14. Secondary outcomes included nightly pain scores, hours of sleep, nighttime awakenings, and Epworth Sleepiness Scores (ESS). Outcomes were recorded daily for 14 days, with formal assessments at baseline and on day 14. Overall, the results of the study revealed that melatonin significantly reduced PROMIS-SD scores (P=0.040) and increased sleep duration on POD2 (P=0.017), although improvements in other outcomes were not statistically significant. These findings suggest melatonin may offer early postoperative benefits in sleep quality following hip arthroplasty.