Background: Hip capsular management after hip arthroscopy remains a topic of debate. Most available current literature is of poor quality and are retrospective or cohort studies. As of today, no clear consensus exists on capsular management after hip arthroscopy. Purpose: To evaluate the effect of routine capsular closure versus unrepaired capsulotomy after interportal capsulotomy measured with NRS pain and the Copenhagen Hip and Groin Outcome Score (HAGOS). Materials and methods: All eligible patients with femoroacetabular impingement who opt for hip arthroscopy (n = 116) were randomly assigned to one of both treatment groups and were operated by a single surgeon. Postoperative pain was measured with the NRS score weekly the first 12 weeks after surgery. The HAGOS questionnaire was measured at 12 and 52 weeks postoperatively. Results: Baseline characteristics and operation details were comparable between treatment groups. Regarding the NRS pain no significant difference was found between groups at any point the first 12 weeks after surgery (p = 0.67). Both groups significantly improved after surgery (p < 0.001). After 3 months follow-up there were no differences between groups for the HAGOS questionnaire except for the domain sport (p = 0.02) in favour of the control group. After 12 months follow-up there were no differences between both treatment groups on all HAGOS domains (p > 0.05). Conclusions: The results of this randomised controlled trial show highest possible evidence that there is no reason for routinely capsular closure after interportal capsulotomy at the end of hip arthroscopy. Trial Registration: This trial was registered at the CCMO Dutch Trial Register: NL55669.048.15.