The main topic of this paper are Czech Interethnic Marriages in Croatia from 1970 to 2015. The paper illustrates the migration of Czechs from the 18th century to the beginning of the 20th century, their integration into the Croatian society, political opportunities, demographic characteristics and the population trends of Czechs in Croatia from 1880 to 2011. Since Czechs in Croatia are concentrated in a specific area, thematic maps of their distribution have been made. The paper sought to respond to the hypotheses and goals that were set out. Interethnic marriages and the structure of these marriages were analyzed to see which nationalities Czechs are mostly married to, in what period and what were the causes of these marriages. Also, the factors influencing the conclusion of interethnic marriages were analyzed (spatial, cultural, political, etc.). Based on the available data, the results show that Czech homogeneous marriages reduced and there is an increasing number of exogenous or interethnic marriages with other nationalities, mostly with Croats as they consist the majority of the overall population, followed by Serbs as the largest ethnic minority in Croatia. It is important to note that very few marriages were concluded with the Slovaks, less than with the Hungarians. Gender -wise, the analysis has shown that female Czechs are more exogenous as they are more involved in ethnically mixed marriages than their male compatriots. When it comes to how children from ethnically mixed marriages categorize themselves, the dominant role of the parent and the emotional impact on their children plays a major role. The child usually takes the nationality of a parent with whom the child is closer. When a community is larger and more populous, children become associated with it, and they become a part of that community. According to the results of this paper and the available data for 1981, twice as many children take the nationality of their fathers than their mothers. There is also a high percentage of children who declare differently than their parents. This is especially reflected in Czech-Croatian families.