Background: Sleep disorders of breathing encompass a spectrum of disorders ranging from primary snoring to obstructive sleep apnea syndrome (OSAS), which leads to septoplasty in the most patients. Objectives: The aim of this study was to evaluate the effects of nasal septoplasty surgery on the severity of OSAS. Methods: The current quasi-experimental self-controlled study was conducted on adult patients with deviated nasal septum and were candidate for nasal septoplasty. Before surgery and two months after surgery, patients underwent respiratory polygraph. The parameters assessed included the airflow and oximetry indices. The severity of sleep apnea will be assessed based on the Apnea-Hypopnea Index (AHI). Also, the severity of snoring was scored from zero to 10 based on the visual analog scale (VAS). The severity of daytime sleepiness was also determined using the Epworth Sleepiness Scale (ESS). Data were analyzed by using SPSS software. Results: There was a significant reduction in the mean score of ESS after the surgery (P<0.001), daytime fatigue (P=0.002), and daytime sleepiness (P<0.001). Also, breathing quality during sleep showed that the severity of apnea (P<0.001), snoring (P<0.001), as well as ESS (P<0001) were significantly improved. There were no significant changes in the means of oxygen saturation (P=0.14) and rapid eye movement (REM) sleep (P=0.06) after non-REM stage 1-2 (P=0.09), but following non-REM stage 3-4 significantly improved (P=0.03). Conclusion: The correction of nasal obstruction improved the general health of OSAS patients. These results further reflected that the corrective surgery could improve the patients’ emotional state and social performance, effectively upgrading their quality of life.