Background: Childhood attention deficit hyperactivity disorder (ADHD) is commonly diagnosed in Saudi Arabia, but there is negligible evidence regarding adult ADHD in college students. Objective: To determine the prevalence and correlates of ADHD among undergraduates at King Abdulaziz University, Jeddah, Saudi Arabia. Methods: In this cross-sectional study, 2280 undergraduate students from 11 colleges at King Abdulaziz University, one of the largest university in Saudi Arabia, were approached in person with a questionnaire that elicited information regarding demographics, education, psychiatric history, health behaviors, and ADHD. A validated Arabic version of the Adult ADHD Self-Report Scale was used. Results: A total of 2059 students (90%) completed the questionnaire (mean age: 21.2 years). Almost one-tenth (11.9%) of the sample met the criteria for adult ADHD; only 6.5% had been diagnosed with ADHD in childhood and <1% (0.8%) had taken medication for the same. Multivariate analyses revealed that high family income, low grade in the last semester, parental divorce, diagnosis of childhood ADHD, prior diagnosis of depression, greater severity of current depression and anxiety, and cigarette smoking increased the likelihood of adult ADHD. Conclusion: A notable proportion of students in this study had suspected adult ADHD. Early evaluation of students with ADHD and identification of those at risk may potentially help in improving their academic performance and quality of life.