This research was conducted in a prison in the northern region of Portugal and aimed at understanding the phenomenon of tattooing in this context. The information collection procedures, namely through semi-directive interviews to inmates, as well as the content analysis of their speeches, resulted in the confirmation of the interdependence between the inmate's age, prison career and tattooing frequency; the connection between hepatitis C virus infection, drug addiction and risk perception regarding the practice of tattooing, and, finally, the elaboration of a set of suggestions for the implementation of harm reduction measures related to tattooing in Portuguese prisons.