Objective: To investigate the rate of ADHD-related traits among young adults in an Australian university, and to examine whether higher endorsement of ADHD-related symptoms is associated with self-reported symptoms of depression, anxiety, distress, and autistic-like traits. Method: In total, 1,002 students aged 17 to 25 years completed the Conners’ Adult ADHD Rating Scale (CAARS), the Depression, Anxiety, and Stress Scale (DASS), and the Autism Quotient (AQ). Results: About 17.3% of students reported “at-risk” levels of ADHD-related symptoms. Regression analyses revealed that CAARS scores explained unique variance in self-reported levels of depression, anxiety, stress, and autism-related traits. Conclusion: The rate of self-reported ADHD symptoms is higher in Australian undergraduate students than that reported in previous studies using the CAARS to investigate rates of diagnosed students. Problems with self-concept accounted for the most unique variance in DASS subscale scores. Hyperactivity/restlessness and inattention/memory problems accounted for the most unique variance in AQ-Social and AQ-Attention-to-Detail scores, respectively.