Purpose <p>Although injection pharyngoplasty (IP) has been well described as a treatment for velopharyngeal insufficiency (VPI) in the pediatric population, there are far fewer studies on its safety and effectiveness in adults with acquired VPI. Our study aims to characterize the safety and efficacy of IP as a treatment for acquired VPI in adults while identifying underlying VPI etiologies and injection characteristics that are associated with positive outcomes.</p> Methods <p>We conducted a retrospective analysis of 30 adult patients with acquired VPI who were treated with IP. We collected data on patient demographics, etiology of acquired VPI, and IP procedural characteristics for analysis. Descriptive statistics are provided for patient demographic and IP procedural characteristics.</p> Results <p>In our cohort, 16 patients had a history of radiation and/or chemotherapy while 14 patients had acquired VPI due to other etiologies. A majority of patients (<i>n</i> = 16) in our study had their VPI resolved with a single injection. Of all 61 injections recorded in our cohort, the most frequent injection agent was calcium hydroxyapatite (<i>n</i> = 35) followed by autologous fat (<i>n</i> = 15). We found that 27 of the patients in our cohort reported improvement in their acquired VPI after IP with only 9 reporting temporary minor complications that were resolved without intervention.</p> Conclusion <p>Our study further establishes IP as a safe and effective procedure for adult patients with acquired VPI.</p>