Phonetics is the study of sounds of human speech, including their production and perception. Orthognathic surgery, on the other hand, is a surgical procedure aimed at correcting skeletal and dental irregularities of jaw and face and following the completion of growth it is indicated in about 25% of patients with cleft lip and palate. Despite the numerous advantages that orthognathic surgery offers for aesthetics and orofacial functions, velopharyngeal structure manipulation may cause impediment of speech in patients with cleft lip and palate. The velopharyngeal mechanism that separates the oral cavity from the nasal cavity during speech may be adversely affected by orthognathic surgery, which causes the maxilla to advance as the hard palate's posterior edge and the soft palate attached to it advance anteriorly. So, the goal of this systematic review is to analyse the change in speech production post orthognathic surgery for correcting midfacial hypoplasia so that if necessary, speech production can be provided post orthognathic surgery.