In the South African context, resource constraints often preclude the comprehensive assessment of large numbers of people for the likelihood of Adult Attention-Deficit/Hyperactivity Disorder (ADHD). Primary screening through a self-report measure may be useful to stream at-risk individuals towards diagnostic assessment services, as well as being useful in population and workplace based research. The present study set out, first, to investigate the usefulness of a self-report ADHD scale to identify at-risk individuals, and, second, to provide preliminary prevalence estimates for Adult ADHD, guided by Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) criteria, in a South African workplace sample. Workers in full-time skilled employment ( N = 1,917), aged 18–44, completed a self-report Adult ADHD scale, and participated in an interview with a psychologist. Their scale data, using three different scoring and interpretation systems, were subjected to statistical analysis. Favourable internal reliability and positive predictive validity were found. Different interpretation systems provided different prevalence estimations: using DSM-5 criteria, a total prevalence estimate of 3.3 % was calculated (attention deficit subtype = 0.9%, hyperactivity-impulsivity subtype = 1.0%, and combined subtype = 1.4%). The positive predictive validity found with this sample suggests that this scale can be used constructively in research or screening contexts to identify at-risk individuals. Furthermore, preliminary prevalence estimates for Adult ADHD, guided by DSM-5 criteria, are now available for a South African workplace sample.