Objective: Laparoendoscopic single-site surgery (LESS) is a new laparoscopy development that avoids the use of multiple ports and minimizes morbidity. Combined with retroperitoneoscopy, LESS is suitable for adrenalectomy. We compared open, conventional laparoscopic, and LESS-retroperitoneoscopic adrenalectomy (LESS-RA) surgeries for adrenal tumor removal. Furthermore, we analyzed the conventional retroperitoneoscopic adrenalectomy (CRA) and LESS-RA outcomes. Materials and Methods: We examined 178 patients who underwent adrenalectomy: 43 by open surgery, 72 by conventional laparoscopy, and 63 by LESS-RA. We analyzed the outcomes of operative time, estimated blood loss (EBL), complications, postoperative convalescence, time to resuming oral intake, analgesics on demand, and hospital stay. Results: We found that the open surgery group had a significantly greater mean EBL than the conventional laparoscopy or LESS-RA group (353.1±313.6 mL vs. 62.3±76.9 mL vs. 60.9±64.3 mL, respectively; p<0.0001). Open surgery was lengthier than LESS-RA. Both hospital stay and time to resuming oral intake were shortest in the LESS-RA group, followed by conventional laparoscopy and open surgery. CRA and LESS-RA did not differ significantly in mean tumor size, operation time, or EBL. However, there were significant differences in postoperative hospital stay length (6.4±3.4 days vs. 3.6±1.3 days, respectively; p<0.0001), time to resuming oral intake (1.2±0.5 days vs. 0.4±0.5 days, respectively; p<0.0001), and number of on-demand intravenous or intramuscular analgesics needed (0.5±0.8 ampoules/vial vs. 0.3±0.6 ampoules/vial, respectively; p=0.0484). Conclusion: The standard approach to adrenalectomy recently improved from open to laparoscopic surgery, transperitoneal to retroperitoneal access, and multiple ports to a single port. Here we found that laparoscopic surgery had better intra- and postoperative outcomes than open surgery. Furthermore, patients treated with LESS-RA required less postoperative recovery time and less analgesic use than those treated with CRA.