There is scant data about the prevalence and correlates of ADHD in middle-income countries. Objective: The aim of this study was to investigate the prevalence and psychiatric correlates of symptomatic ADHD in a large metropolitan area of a middle-income country. Methods: An in-person household survey with randomly selected 2,297 adults aged 19 to 60 from Rio de Janeiro, Brazil, assessed by trained lay interviewers. The Adult Self-Rating Scale Screener (ASRS-6) was used. Chi-square and logistic regression were conducted. Results: ADHD prevalence was 4.59 (95% CI [3.56, 5.44]). Those with ADHD were younger and more often unemployed; they displayed more psychiatric symptoms (depression, anxiety, and alcohol abuse) and a history of bullying and sexual abuse. They also had worse physical health indicators. Findings remained significant when controlling for socioeconomic variables. Conclusion: Adults with symptomatic ADHD from a large metropolitan area in Brazil show a pattern of findings consistent with what has been observed in higher-income countries