Background Temperament has been increasingly studied in relation to neurodevelopmental disorders, including Attention-Deficit/Hyperactivity Disorder (ADHD). This study examines the association between ADHD and affective temperament traits using the Temperament Scale of Memphis, Pisa, Paris, and San Diego (TEMPS-A) in a clinical outpatient sample in Beirut, Lebanon. Methods This cross-sectional study included 2,564 psychiatric outpatients aged 15 or older who completed the TEMPS-A. ADHD diagnosis was determined through clinical assessments based on the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria. Statistical analyses included descriptive comparisons and multivariate logistic regression, with temperament trait scores categorized based on Lebanese population norms. Results Participants had an average age of 38.53 years, with females comprising 52.3 % of the sample. Bivariate analyses showed ADHD was associated with higher cyclothymic (CT), hyperthymic (HT), and irritable (IT) temperament trait scores. After adjusting for age, gender, and comorbidities, only IT remained a significant risk factor for ADHD (OR = 2.73, 95 % CI: 1.23–6.09), while depressive temperament trait (DT) emerged as a protective factor (OR = 0.38, 95 % CI: 0.17–0.87). Conclusion Our findings highlight the complex relationship between temperament traits and ADHD. IT was a significant risk factor, while DT unexpectedly appeared protective. These results underscore the need for further investigation into temperament traits as a diagnostic and therapeutic consideration in ADHD.