The history of the middle-aged Dalmatian communes of Split and Poljica has been a subject of numerous researches, but only in an isolated manner. Therefore, this diploma paper sets out to present the inevitable contact of the two communities as a result of their geographical proximity. The paper offers the historical overview of the communes of Split and Poljica among which the latter was in a tribal organisational form. The analysed period comprised 14th and 15th century because these centuries were marked by a rather intense contact of the two aforementioned communities. A rather significant mediatory role of Church is portrayed in the presentation of its impact on the relations of the inhabitants of both communes. Despite the conflicts regarding the lands, the relations among inhabitants and the assimilation to the middle-aged commune of Split was inevitable. The city of Split included the cultural influence of the Poljica commune in its history and the communes established a mutually beneficial cooperation.