Abstract Objectives: In patients with chronic rhinosinusitis (CRS), olfactory dysfunction (OD) is a common complaint. The focus of this research was to evaluate the effectiveness of olfactory training (OT) in patients with CRS after sinonasal surgery. Design : Prospective controlled trial. Participants: We enrolled 111 Korean CRS patients who underwent sinonasal surgery. Main Outcome Measures: At baseline and three months after starting OT, both participants were assessed by an olfactory function test and endoscopy. The Korean version of the Sniffin’ stick II (KVSS-II) was used to perform the olfactory function test. A visual analog scale and the Mini-Mental State Examination were used to assess nasal and psychological functions. Over the course of three months, five odorants were used in OT (rose, lemon, cinnamon, orange, and peach). Results: Over a 12-week duration, OT increased olfactory activity in nearly 62 percent of subjects than in non-OT subjects. The OT group had significantly higher olfactory outcomes for the total KVSS-II and identification scores than the non-OT group between the initial and follow-up assessments. The initial score influenced the degree of olfactory improvement after OT. Conclusions: OT patients exhibited significantly higher total KVSS-II scores compared with non-OT patients after sinonasal surgery; in particular, the odor identification score was different between the two groups. The results of this study show that a 12-week period of repeated short-term exposure to various odors could be useful in enhancing olfactory activity in patients who underwent sinonasal surgery for the improvement of sensory-neural olfactory impairment.