The study focuses on understanding the opportunities to improve the prevention of religious extremism in penitentiary institutions. Analysis of factors in the spread of religious extremism and measures of its prevention not only raises the efficiency of a country’s penitentiary system but promotes the stability of social relations and increases the security of the population. The goal of the study is to propose directions for the improvement of the religious extremism prevention system to enhance the efficiency of a country’s penitentiary system. The study examines the features of the dissemination of extremism and terrorism and explores the penitentiary practice of detention of persons convicted of extremist crimes in the Republic of Kazakhstan. According to the results of the expert survey, factors in the spread of religious extremism in Kazakhstan’s penitentiary system are identified and recommendations for possible measures to prevent them are offered. The authors argue that such prevention should strengthen interaction with religious departments and public organizations dealing with religious extremism, introduce international programs into the work of penitentiary employees, include training in special programs of psychologists and theologians, involve authoritative representatives of the clergy, and introduce the institution of chaplains. The presented theoretical and practical recommendations will enable government agencies to curb the spread of religious extremism in penitentiary institutions.   Received: 4 February 2023 / Accepted: 22 April 2023 / Published: 5 May 2023