Herein we present simple methods to prevent postoperative inguinal hernia (IH) after extraperitoneal and transperitoneal robot-assisted radical prostatectomy (RARP). Among 275 patients who underwent RARP between January 2014 and December 2016 at our institution, we evaluated 143 and 115 patients who underwent extraperitoneal-RARP (e-RARP) and transperitoneal-RARP (t-RARP), respectively, after excluding those with intraoperative detection of IH (17 patients). In the e-RARP group, all 143 patients (286 groins) underwent an IH prevention procedure. In the t-RARP group, the first 22 patients (44 groins) did not undergo an IH prevention procedure, whereas 29 patients (37 groins) with patent processus vaginalis (PPV) among the last 93 patients underwent the procedure. The IH prevention procedure during e-RARP included release of the vas deferens from the peritoneum and spermatic cord, and peritoneal dissection of the spermatic cord at the internal inguinal ring. The IH prevention procedure during t-RARP included release of the vas deferens from the peritoneum and spermatic cord, complete circumferential dissection of the peritoneum around the PPV at the level of the internal inguinal ring, and ligation of the PPV with a Hem-o- Loc○R clip. In the e-RARP group, postoperative IH occurred in 3 of the 143 patients (1.9%) during the follow-up period of 22.0±9.2 months. In the first subgroup of t-RARP, postoperative IH developed in 4 of the 22 patients (18%) during the follow-up period of 33.1±12.1 months, whereas in the last t-RARP group, postoperative IH developed in 3 of the 93 patients (3.3%) during the follow-up period of 20.1±8.6 months. Different IH prevention procedures performed in patients undergoing e-RARP and t-RARP were simple and effective in preventing postoperative IH.