There is insufficient information available regarding the psychopathological characteristics of the prison population in low-middle-income countries. This study aimed to estimate the current prevalence of psychiatric symptoms and pathological personality traits among sentenced male prisoners from two Ecuadorian prisons. A sample of 675 individuals aged 18-75 years (M= 35.58; SD= 10.57) was assessed using the Spanish adaptation of the Personality Assessment Inventory (PAI). Current prevalence was 69.9% for at least one of the studied clinical syndromes. The most prevalent clinical syndromes were Alcohol problems (33.6%), Mania (32.3%), Drug problems (27.9%), Antisocial features (23.8%), Paranoia (21.4%), Schizophrenia (19.5%), and Somatic complaints (17.7%). Comorbidity was found in 49.8% of the sample. Taken together, Alcohol problems and Drug problems accounted for the highest prevalence (55.8% to 71.4%) among individuals with clinically significant scores in each of the syndromes analyzed. Further studies regarding the influence of the variables related to the prison context on the mental health of inmates will increase the usefulness of the findings.