International law ensures that states actively participate in incorporating human rights into national legislations. Human rights are the most significant achievement of civilization, and even though they are guaranteed, they are not equally respected everywhere. Given that various factors, with political nature being the most crucial, affect the level of respect for human rights, it is essential to emphasize the necessity of upholding these rights when an individual's freedom is deprived. Depriving a person of this right places the prisoner in a disadvantaged position in society, the institution in which they reside, and with the people with whom they have direct contact. Such circumstances impact the psychophysical development of the individual. In Western civilization, the idea of punishment with the aim of reintegrating the offender into society has been adopted. The principles of rehabilitation have influenced the state's relationship with prisoners and directly their rights. With the development of international standards, a branch of law called penitentiary law has evolved, dealing with the protection of prisoners' rights while ensuring that their stay in prison is carried out with respect for human dignity and physical and psychological integrity. Accordingly, the author, after introductory considerations, addresses the issue of international standards for prisoners' rights and their implementation in the Republic of Croatia. The development of prisoners' rights throughout history is presented since this is a relatively young legal matter. Relevant international legal sources and their supervisory mechanisms are discussed, with particular attention to soft law documents, as they are the only ones that comprehensively address prisoners' rights in practice and the possibilities of their violation. Additionally, the author examines the application of these standards in the Republic of Croatia based on the European Convention for the Protection of Human Rights and Fundamental Freedoms and the practice of the European Court of Human Rights. In the final section, an assessment of the state of prisons and penitentiaries in the Republic of Croatia is provided based on the evaluations of international bodies, and the analysis can be considered comprehensive, resulting in a constructive assessment of the application of rights in practice.