World migration is gaining ever greater and significant volume and tends to spread to new areas. Considering the hostile attitude of the domestic population to the newcomers at the very beginning, it is understandable that the same attitude will get even greater if the behavior of the newcomers disturbs the balance in society at the local and state levels. In addition, strengthening anti-immigrant policies across Europe is fueling intolerance towards foreign nationals, which greatly hampers the possibility of their integration or reintegration. By addressing the negative aspects of immigrant adaptation, there are given examples of their inappropriate lifestyle in relation to the social norms of the community they immigrated and their offenses, that is, criminal offenses in a new environment. This paper deals with issues of immigrants, ie persons of foreign nationality, who are at the same time perpetrators of criminal offenses and their adaptations, both in social and prison terms. Worldwide, there are examples of non-compliance with fundamental human rights, inhumane and undignified treatment in the treatment of prisoners of foreign nationals, which is in violation of many provisions of conventions and laws, inadequate conditions for serving prison sentences and various segregations in penitentiary institutions. The statistical increase in the number of foreign nationals in the Croatian territory has been caused by Euro-Mediterranean migration waves, and there has been an increase in the number of foreign nationals in penitentiary institutions. Although no such research has been carried out in the Republic of Croatia, the aforementioned findings point to the need for its implementation and for timely adaptation of penal conditions and policies to emerging changes.