Background <p>The primary aim of this study was to investigate, using ultrasonography (USG), the relationship between masseter muscle thickness (MMT) and sagittal skeletal pattern (SSP). In addition, the study aimed to assess the potential relationships between MMT and variables such as age, sex, and body mass index (BMI).</p> Methods <p>This study was designed as a prospective cross-sectional investigation conducted at the Department of Oral and Maxillofacial Radiology in our institution, between January 2024 and December 2024. Lateral cephalometric radiographs of 101 patients (45 men and 56 women; mean age, 24.71) were included. The main variables assessed were MMT, SSP, intermolar distance, BMI, age, and sex.</p> Results <p>MMT was significantly greater in Class III individuals compared to those in Class I and II (<i>p</i> &lt; 0.05). No significant association was found between MMT and age group. However, MMT was significantly higher in males than in females. A moderate positive correlation was observed between MMT and BMI (<i>r</i> ≈ 0.4), and a weak positive correlation with intermolar distance (<i>r</i> ≈ 0.2).</p> Conclusions <p>MMT is significantly associated with SSP and sex, and moderately correlated with BMI. These results can suggest that MMT may provide useful adjuncts in SSP assessment and orthodontic planning.</p> Trial registration <p>This trial registered at clinicaltrial.gov (registration number/date: NCT06870084/March 10, 2025).</p>