While the last decade has seen a growth of support for harm reduction around the world, the availability and accessibility of quality harm reduction services in prison settings is uneven and continues to be inadequate compared to the progress achieved in the broader community. This article provides a brief overview of harm reduction in prisons in Catalonia (Spain), Greece, Ireland, Italy, Latvia, Poland, and Portugal. While each country provides a wide range of harm reduction services in the broader community, the majority fail to provide these same services or the same quality of these services, in prison settings, in clear violation of international human rights law and minimum standards on the treatment of prisoners. Where harm reduction services have been available and easily accessible in prison settings for some time, better health outcomes have been observed, including significantly reduced rates of HIV and HCV incidence. While the provision of harm reduction in each of these countries' prisons varies considerably, certain key themes and lessons can be distilled, including around features of an enabling environment for harm reduction, resource allocation, collection of disaggregated data, and accessibility of services.