Objective. Investigate the association between formants frequencies and length and sagittal projection of the maxilla and mandible. Study Design. Cross-sectional study. Method. A total of 47 consecutive patients were recruited. Craniofacial measures included; maxillary length (ANS-PNS), mandibular length (Co-Gn), relationship between maxilla and mandible in the sagittal plane (ANB), the sagittal projection of the maxilla (SNA), and mandible (SNB). Subjects were asked to phonate vowels /a/, /i/, /o/, and /u/. Measurements were made in real-time and formant frequencies across F1, F2, F3, and F4 were determined. Results. There was a significant negative association between the length of the maxilla and F4 for all the vowels, and a significant negative association between the length of the mandible and F4 for vowels /o/ and /u/. The length of maxilla and mandible also negatively associated with F3 for vowels /a/, /i/, /o/, and vowels /i/, /o/, and /u/ respectively. For the first two formants, the negative association was less pronounced. Conclusion. There was a significant negative association between the formant frequencies F3, F4, and the length of the mandible and maxilla for vowels /a/, /i/, /o/, and /u/.