Prison populations are disproportionally affected by communicable diseases when compared with the general community because of a complex mix of socioeconomic determinants and environmental factors. Tailored and adequate health care provision in prisons has the potential to reach vulnerable and underserved groups and address their complex needs. We investigated the available evidence on modalities and effectiveness of active case-finding interventions in prisons by searching PubMed, Embase, and the Cochrane Library for records on prison and active case finding with no language limit. Conference abstracts and unpublished research reports also were retrieved. We analyzed the findings by testing modality, outcomes, and study quality. The included 90 records-63 peer-reviewed, 26 from gray literature, and 1 systematic review-reported variously on viral hepatitis, human immunodeficiency virus, sexually transmitted infections, and tuberculosis. No records were retrieved for other communicable diseases. Provider-initiated opt-in testing was the most frequently investigated modality. Testing at entry and provider-initiated testing were reported to result in comparatively higher uptake ranges. However, no comparative studies were identified that reported statistically significant differences between testing modalities. Positivity rates among tested inmates ranged broadly but were generally high for all diseases. The evidence on active case finding in correctional facilities is limited, heterogeneous, and of low quality, making it challenging to draw conclusions on the effect of different testing modalities. Scale-up of provider-initiated testing in European correctional facilities could substantially reduce the undiagnosed fraction and, hence, prevent additional disease transmission in both prison settings and the community at large.