Abstract Purpose One of the most common complications after septoplasty is a postoperative infection. We investigated the number of postoperative infections and unplanned postoperative visits (UPV) in septoplasties with and without additional nasal surgery at our institution and evaluated the role of antibiotic prophylaxis. Methods We collected data of all consecutive 302 septoplasty or septocolumelloplasty patients operated during the year 2018 at the Department of Otorhinolaryngology-Head and Neck Surgery, HUS Helsinki University Hospital (Helsinki, Finland). Hospital charts were reviewed to record sociodemographic patient characteristics and clinical parameters regarding surgery and follow-up. Results Altogether 239 patients (79.1%) received pre- and/or postoperative prophylactic antibiotics and within this group 3.3% developed a postoperative infection. The infection rate in the non-prophylaxis group of 63 patients was 12.7% (p = 0.007). When all patients who received postoperative antibiotics were excluded, we found that the infection rate in the preoperative prophylaxis group was 3.8%, as opposed to an infection rate of 12.7% in the non-prophylaxis group (p = 0.013). When evaluating septoplasty with additional sinonasal surgery (n = 115) the rate of postoperative infection was 3.3% in the prophylaxis group and 16.7% in the non-prophylaxis group (p = 0.034). These results show a statistically significant stand-alone effect of preoperative prophylactic antibiotics in preventing postoperative infection in septoplasty, especially regarding additional sinonasal surgery. Conclusion The use of preoperative antibiotics as a prophylactic measure diminished statistically significantly the rate of infections and UPVs in septoplasty when all postoperative infections, superficial and mild ones included, were taken into account.