In this research we aimed to (1) develop and validate a new questionnaire examining attitudes and knowledge towards medical genetics, (2) examine the knowledge and attitudes towards medical genetics in students of the Medical Faculty in Rijeka, Croatia and (3) evaluate the impact of education from the mandatory course Medical Genetics on the change of knowledge and attitudes. The study was conducted on 191 fifth- and sixth-year students of the Integrated Undergraduate and Graduate University Study of Medicine in the academic year 2019/2020. Students completed the validated online questionnaire anonymously and voluntarily. Fifth-year students completed the questionnaire twice (beginning/end of the course), while sixth-year students completed the questionnaire once, 3 months after completing the course. The education was carefully designed for medical students according to the CoreCompetences in Genetics for Health Professionals in Europe issued by the European Society of Human Genetics. Using the Kruskal-Wallis test, a statistically significant difference was found between fifth year before and after education and between the fifth year before education and sixth year for (a) total knowledge (P < 0.001), (b) total attitudes (P < 0.001) and (c) personal assessment of knowledge in medical genetics (P < 0.001). Moreover, positive attitudes were associated with higher levels of knowledge. In conclusion, our results emphasise the importance of needs-based education in medical genetics for medical students, which is indispensable for the increase in the level of knowledge and development of positive attitudes in order to provide better health care for patients with genetic disorders.