The most prominent characteristic of adult attention deficit hyperactivity disorder (ADHD) is impulsive behavior and deficits in executive functions, which require long-term organization and discipline. This may have serious implications in terms of adherence to treatment among adults living with HIV (PLWH). This study aimed to determine the prevalence of ADHD among non-perinatally infected PLWH and its effect on adherence to antiretroviral treatment (ART) and scheduled appointments. The PLWH admitted to our centers between January 2012 and February 2016 were invited to the study. ADHD diagnosis was made according to the novel criteria guided interviews. The first ART interruption for ≥ 6 days per month (≤ 80%) was defined as ''ART-event'' and the first non-attendance of any scheduled appointment was defined as ''appointment-event''. Kaplan-Meier plot with a Log-rank test was used for event-free adherence (EFA). Twenty-five patients out of 85 were diagnosed with ADHD (29.4 %) which was significantly higher than the highest percentage reported (7.3 %) for the general population (p < 0.0001). Both ART-event (p = 0.0002) and appointment-event (p = 0.02) were significantly higher among ADHD participants compared to those without. Additionally, both ART-EFA (p = 0.00014) and appointment-EFA (p = 0.023) were significantly shorter among ADHD participants compared to those without. ADHD is significantly higher in adult PLWH and people with ADHD had a significant tendency for non-adherence to ART and follow-up. Screening for ADHD as well as providing treatment when required would be beneficial to achieve and maintain virologic success.