From both a social and epidemiological perspective, incarcerated individuals in Latin America face a series of accumulated disadvantages in different areas, one of them being the deterioration in their mental health linked to confinement and the negative effects of incarceration. However, since mental health evaluations at the intake phase are virtually non-existent for incarcerated populations in Chile, the diagnosis of, monitoring of, and intervention initiatives on mental health issues are very limited, thus limiting the possibilities of causal relationship analysis and evidence-based interventions. Thus, the first step to making the topic of mental health more visible to public policy is to gather more evidence about it in prison settings. This article analyzed—using a screening approach—the presence, suspicion, or absence of psychopathology using the GHQ-12 instrument among a sample of 1159 incarcerated individuals grouped in 20 prisons throughout Chile. Our main results show that there are about 22.3% of Chilean inmates with presence of some form of psychopathology, plus an additional 51.8% with the criteria for suspected psychopathology; we also found significant, bivariate relationships between various mental health items and gender, the type of prison, and age, so that incarcerated women, younger inmates, and those housed in public prisons reporting more problems than their counterparts. Finally, we discuss the implications of our findings for the improvement of prison life in Chile and the possibility of social reintegration for incarcerated people.