Purpose: Because of the high number of patients with chronic pain following inguinal hernia repair, a new, simple and safe method of repair is needed. Onstep is a new type of inguinal hernia repair that might be able to reduce postoperative acute and chronic pain. The aim of this study was to investigate if there were differences in early postoperative pain during the first 10 days between the Onstep and the Lichtenstein technique. Methods: This was a double-blinded, randomized clinical trial conducted in five surgical departments in Denmark, from April 2013 to June 2014. Eligible participants for this study were male patients, >18 years, with a primary inguinal hernia. Experimental treatment in this study was the Onstep technique, which was compared with the Lichtenstein repair. Primary outcome was postoperative pain during the first 10 days following surgery. Secondary outcomes included duration of surgery, period for return to normal daily activities (days), and recurrence. Randomization was done in blocks and stratified on centers. Participants and study personnel handling questionnaires and analysis were blinded to the allocation. Results: In total, 290 participants were randomized. We found no significant differences between the groups regarding early postoperative pain or minor postoperative complications. Four patients had a recurrence within the first 10 days of follow-up, one patient in the Lichtenstein group and three patients in the Onstep group, p = 0.30. Conclusion: The Onstep technique for inguinal hernia repair was safe and had comparable results to the Lichtenstein repair regarding short-term pain and postoperative complications. Trial registration: Clinicaltrials.gov (NCT01753219).