This graduate thesis examines the cooperation of professional associates and teaching assistants employed in regular elementary schools in the Republic of Croatia. In the theoretical part of the paper, the legislative framework for the work of professional associates and teaching assistants, as well as their cooperation, is presented. The empirical part of the work brings qualitative research, the goal of which was to detect different forms of cooperation between teaching assistants and professional associates, and to analyze their frequency and effectiveness from the perspective of teaching assistants. The research was conducted using the online written interview method on a sample of 32 teaching assistants. The results of the research show that teaching assistants emphasize conversation as the most common and effective method of cooperation, followed by meetings, e-mail communication and messaging. Although the conversation is the most positioned with regard to frequency and efficiency, the largest number of suggestions for improving cooperation with professional associates was about communication. Teaching assistants would like it to be of higher quality, more open and more frequent, with many of them encouraging more frequent meetings and additional professional development. At the end of the paper, certain limitations of this research are stated, as well as the importance of certain topics generated on the basis of this research (for example, the status of assistants in the school team) which can serve as guidelines for future research on this current research topic in the national pedagogical context.