This study aimed to characterize mental health service access in metropolitan Lima, Peru. Between May and December 2012, we interviewed 4,445 Peruvian adults, applying the Mini-International Neuropsychiatric Interview (MINI); a modified version of the WHO Disability Assessment Schedule (WHODAS-S); and, a health services access questionnaire. In the prior year, 3.6% (95% CI 3.0–4.4) of respondents accessed mental health services. Care access was associated with female sex; being unemployed; and having a diagnosed psychiatric morbidity. Of those with psychiatric morbidity, 16.9% (95% CI 13.3–21.3) received clinical care. Care access was 25.8% (95% CI 19.9–32.8) for people with a depressive episode; 12.1% (95% CI 7.4–19.2) for any anxiety disorder; and, 5.9% (95% CI 1.7–18.6) for harmful alcohol consumption or dependence. Respondents with moderate to severe levels of disability were more likely to recognize the need for care, but this was not necessarily associated with higher care access. Reducing the mental, neurological and substance use disorders treatment gap in Peru are discussed in light of the findings.