Introduction  Peritoneal antibiotic or normal saline lavage is seen to be beneficial in order to reduce the pain or infection risk through laparoscopic surgeries. It can also be applied for laparoscopic colectomy surgeries. In this study, we have compared the effects of antibiotic solution lavage (gentamycin-clindamycin) with normal saline lavage in patients undergoing laparoscopic colectomy surgery. Method  In this double-blind Randomized Controlled Trial (RCT), 40 patients undergoing laparoscopic colectomy surgery were divided into antibiotic and normal saline lavage groups (20 patients in each group). Post-operational pain, need for painkiller, white blood cells count, C-reactive protein level, duration of hospitalization and wound infection were compared in 30 days between the groups. Results  Antibiotic lavage group had significantly less pain than the normal saline group (p < 0.05) through 3, 6, 12 and 24 h after surgery. C-reactive protein level, white blood cells count, painkiller use, and hospitalization duration were significantly lower in antibiotic group. However, there was no difference regarding wound or intra-abdominal infection between the both groups. Conclusion  Using gentamicin-clindamycin peritonea lavage helps patients undergoing laparoscopic colectomy surgery in pain reduction, need for painkillers and hospitalization duration.