Context: Mental health is a central aspect of public health and social development, as such it corresponds to target 3.4 of the Sustainable Development Goals. This target aims to promote mental health and well-being, making it especially necessary to address this matter in environments such as prisons where exposure to risk factors is high. Incarceration itself is a cause of mental illness. Central and Eastern European countries hold some of the highest prison populations in the region and Poland numbers in this regard are 50% higher than the average in the European Union (EU) (about 179 inmates per 100,000 inhabitants). In Polish prisons, the chance of receiving adequate psychiatric and psychological care is limited due to a shortage of trained personnel and scarce infrastructure. However, data on mental health in Polish prisons is not routinely reported from official sources. Article 150 of the Polish Penal Code attempts to protect the mental health of inmates; yet, in reality, there is no legal enforcement to apply these measures, a feature shared with most of its neighbouring countries. The aim of this policy brief is to offer recommendations to lower recidivism rates, up-scale prison staff and create spill-over effects on (mental) healthcare and security in Polish prisons.Policy Options: The World Health Organization (WHO) European Framework for Action on Mental Health 2021-2025 should be adapted to the Polish Prison System. Best practices focus on a collaborative approach centred on healthcare services, labour policies, well-being and rehabilitation. Ideally, incarceration provides inmates with the possibility to be included and active, to see their relatives, to vote, to be engaged and maintain contact with the outside society. These best practices statistically reduce mental illnesses, lower recidivism and promote inclusion and rehabilitation. Recommendations: To tackle mental health challenges that prisoners in Poland experience, it is recommended to adapt a new approach with the following components: improving methodological quality of data collection as well as routine reporting to enable good governance structures, promoting collaborative efforts among stakeholders, and strengthening existing resources through capacity building which has been convincingly demonstrated as the most cost-effective type of interventions.