Aim: To investigate factors determining the need for general anesthesia (GA) to deliver dental treatment for adult people with intellectual and developmental disabilities (IDD). Methods: This study involved a retrospective review of medical records of adult patients with IDD who received dental treatment under GA at Tabuk Specialist Dental Center, Saudi Arabia, between 2018 and 2020. Demographic characteristics and dental-related details, level of cooperation, and methods of delivering dental treatment were collected. Results: A total of 86 adult patients with IDD were included. The mean age of the study participants was 34.8 years (standard deviation [SD] 6.5), and the majority were males ( n = 47, 54.7%). Eighteen patients had aphasia (20.9%), 16 had epilepsy (18.6%), and 10 had cerebral palsy (11.6%). Most dental treatments delivered were complex dental treatments ( n = 39, 45.3%) followed by dental extraction ( n = 25, 29.1%), and non-surgical periodontal therapy ( n = 22, 25.5%). Females had higher odds of undergoing GA compared to males (Odds ratio (OR) =6.79, 95% Confidence intervals (CI): 1.62–28.41). Furthermore, patients who had aphasia had higher odds of undergoing GA compared to patients who had no medical conditions (OR = 14.03, 95% CI: 1.05–186.7). Conclusion: Being female or having aphasia are independent factors related to the need for GA to deliver dental treatment for Saudi adults with IDD.