Research regarding mental illness and drug addiction among inmates in Morocco requires increased knowledge; previous literature reported that prisoners suffer from severe psychological distress. The present study aimed to provide information about Moroccan prisoners’ psychological distress and define the differences in psychological distress levels among inmates with and without drug-dependence. A sample of 177 male inmates completed a set of surveys, including the Drug Use Disorders Identification Test (DUDIT) and the Brief Symptom Inventory (BSI). The “Drug dependence” group scored significantly higher psychological distress levels in each of the BSI domains. The strongest differences were measured in the General Severity Index (GSI), hostility, and depression scales. Moroccan prison inmates have high psychological distress, and those with drug-dependence have even higher. There is a need of psychiatric assessment, selection, and care possibilities in prison inmate populations.