Introduction: Sexual and reproductive health is a critical aspect of medical education, yet significant knowledge gaps persist even among future healthcare professionals. This study aimed to evaluate the knowledge, behaviors, and attitudes of Romanian medical students regarding sexually transmitted infections (STIs) and contraceptive practices. Materials and Methods: A cross-sectional observational study was conducted on 510 undergraduate medical students, using a validated 30-item online questionnaire assessing socio-demographic data, sexual behaviors, STI knowledge, and attitudes towards sexual health. Descriptive statistics, chi-square, and Spearman correlation tests were used to analyze the data. Results: Participants demonstrated a good understanding of common STI pathogens and transmission routes, with 99.02% identifying unprotected vaginal intercourse as a risk factor. However, only 58.82% correctly identified Chlamydia trachomatis, and awareness of less common pathogens remained low. Long-term complications such as infertility (85.29%) and cervical cancer (87.25%) were well recognized, although misconceptions about STI severity persisted, with over 40% believing that STIs are not dangerous because they are treatable. Male students reported earlier sexual debut and more frequent high-risk behaviors, while females were more likely to consult specialist doctors and receive HPV vaccination. The level of knowledge correlated positively with parental education and faculty program. Conclusions: Despite generally high awareness of STI-related topics, considerable gaps and misconceptions persist among Romanian medical students. These findings highlight the need for comprehensive, structured sexual health education integrated into medical curricula to ensure future healthcare providers are well-equipped to promote public health.