Objective The authors wanted to examine the association between attention deficit hyperactivity disorder (ADHD) and personality characteristics and the potential mediating role of these characteristics in the relationship between ADHD and depression in older adults in the general Dutch population. Methods Data from the Longitudinal Aging Study Amsterdam in 2008/2009 were used in a cross-sectional design on 231 participants with and without ADHD aged 60-94 years. Questionnaires assessing self-esteem, self-efficacy, mastery, neuroticism, and social inadequacy were administered. ADHD was measured by means of ADHD diagnosis and level of ADHD symptoms. Linear regression analyses were performed to assess the association between ADHD (symptoms) and personality characteristics. Single and multivariate mediation analyses were performed to examine the mediating role of personality characteristics in the relationship between ADHD (symptoms) and depressive symptoms. Results ADHD was significantly negatively associated with sense of mastery (B =-2.44, t =-3.14, df = 228, p = 0.002), self-esteem (B =-1.16, t =-2.27, df = 228, p = 0.02), and self-efficacy (B =-2.33, t =-2.02, df = 228, p = 0.045) and positively associated with neuroticism (B = 0.99, t = 4.90, df = 228, p <0.001) and social inadequacy (B = 0.65, t = 3.32, df = 229, p = 0.001). In the single mediation analyses, all personality characteristics were mediators in the relationship between ADHD symptoms and depressive symptoms. In the multivariate analysis only mastery and self-esteem were mediators. Conclusion Older adults with ADHD reported lower self-esteem and sense of mastery and higher levels of neuroticism and social inadequacy than older adults without ADHD. Mastery and self-esteem partly explained the association between ADHD and depressive symptoms in old age. The results implicate that in treatment clinicians should pay attention to the personality characteristics of older adults with ADHD.