Background: Medical students should have adequate knowledge and positive attitudes toward breastfeeding to support breastfeeding dyads. No studies in Croatia have explored breastfeeding knowledge, attitudes or intentions among medical students. Research Aim: To investigate breastfeeding knowledge, attitudes and intentions among medical students at the University of Split School of Medicine. Methods: A cross-sectional study was conducted from March to April 2023, using online and written questionnaires. All medical students without children were eligible to participate. The validated Breastfeeding Intentions, Attitudes, and Knowledge Questionnaire (BIAKQ) was used. Sociodemographic data were collected. Analysis was conducted using descriptive statistics, t tests, and Mann-Whitney U test. Results: A total of 357 medical students participated (response rate 64.1%). There was no significant difference between preclinical and clinical students. Students who attended the elective “Breastfeeding Medicine” demonstrated significantly more positive attitudes toward breastfeeding (Mean Rank = 215.62) than those who did not attend (Mean Rank = 173.58; U= 5468.50, p = 0.010); however, no significant difference was found in knowledge or intentions. Female students had significantly more positive attitudes compared to male students (Mean Rank = 189.47 vs. Mean Rank = 150.55, U = 9796.50, p = 0.001), whereas male students expressed significantly more positive intentions ( M = 36.97, SD = 5.26 vs. M = 34.44, SD = 5.86, t = −3.69, p = 0.002). The mean knowledge score was 11.92 ( SD = 1.43) out of 13 points. Negative attitudes towards breastfeeding beyond 1 year and breastfeeding in public were found. Conclusion: Despite adequate breastfeeding knowledge, some medical students demonstrated negative attitudes and intentions toward breastfeeding. Including breastfeeding education into core medical subjects focusing on the importance of breastfeeding for maternal and infant health and the risks of formula feeding could help improve attitudes, especially during the clinical years. It would also be important to address prevailing prejudices.