Introduction: HIV is a virus that attacks the immune system, specifically CD4+ T lymphocytes, the key cells of the immune system. No medicine has been developed so far for HIV and that is why this infection is considered a chronic disease due to the effectiveness of antiretroviral therapy. If the HIV infection is not treated, acquired immunodeficiency syndrome (AIDS) occurs. HIV can be transmitted through sexual contact, during pregnancy and childbirth, and through reusable medical equipment or drug use equipment. Methodology: the study was carried out at the Faculty of Health Studies of the University of Rijeka during April 2024. 100 first- and third-year nursing undergraduate students participated in the research. Students of both genders, study status (full-time and part-time), different ages and years of study participated. The questionnaire was created in a Google form and consists of 29 questions, 7 of which are sociodemographic and 22 about the transmission of HIV infection. The results: the research results showed that hypotheses 1 and 2 were accepted because there were no significant differences in the results. Hypothesis 3 was rejected because there is no statistically significant difference in knowledge about the transmission of HIV infection between 3rd year regular and 3rd year part-time undergraduate nursing students at the Faculty of Health Studies in Rijeka. Discussion: this research aims to assess the level of knowledge among undergraduate nursing students at the Faculty of Health Studies in Rijeka about the transmission of HIV infection. We chose the topic of the final paper and research for the reason that it is not present in everyday conversations, and it is avoided to talk about it, and it is important to point out the importance of the transmission of HIV infection. The research was conducted at the Faculty of Health Studies of the University of Rijeka in April 2024.