Purpose <p>To assess sinonasal function after preservation maxillomandibular advancement (MMA), as initial reports have shown it may decrease postoperatively.</p> Methods <p>This prospective study was performed at a tertiary referral center starting January 2023. MMA was performed with previously published nasal modifications to help mitigate negative sinonasal outcomes. Sino-nasal Outcome Test (SNOT-22) and Nasal Obstruction Symptom Evaluation Survey (NOSE) were collected preoperatively, and one and three months postoperatively. Repeated measures ANOVAs with a Bonferroni adjustment were performed for total score, total sinonasal score (sum of questions 1–12), and each symptom. Both <i>p</i>-values and partial eta squared (n_p²) were reported.</p> Results <p>Twenty patients were included. Median age was 50.7 years (range 31–65), with 20.0% being female. Preoperative AHI (65.1 ± 28.9) and SpO2 Nadir (78.0% [69.0–82.0]) improved to 12.1 ± 12.1 and 86.0 ± 3.2%. NOSE significantly decreased at one month (55.9 ± 28.4 vs. 8.11 ± 12.0, <i>p</i> &lt; 0.001). Total score and total sinonasal scores significantly decreased postoperatively (49.0 ± 21.6 vs. 18.1 ± 17.4 vs. 12.5 ± 14.1, <i>p</i> &lt; 0.001; 17.3 ± 12.5 vs. 9.2 ± 9.3 vs. 6.3 ± 7.3, <i>p</i> = 0.003) with MMA having large effects on both variables (n_p²=0.72 and 0.35, respectively). MMA had large significant effects on improvement in need to blow nose, nasal blockage, sneezing, runny nose, cough, post-nasal discharge, dizziness, and ear pain at one and three months postoperatively. Facial pain/pressure significantly worsened at one-month but then improved to baseline at three months postoperatively ((1.2 ± 1.4 vs. 1.9 ± 1.5 vs. 1.2 ± 1.4, <i>p</i> = 0.026).</p> Conclusion <p>Patients who underwent preservation MMA did not show evidence of worsening sinonasal function, with some evidence that sinonasal function may improve after MMA at three months postoperatively. Long-term follow-up with more patients is needed to support these findings.</p>