Abstract Background The increasing number of cancer cases diagnosed at young ages and the impact of the disease and treatments on reproductive function have led to the development of Oncofertility. While oncologists typically lead these discussions, family doctors, as primary care providers, also play a crucial role. This study aims to assess family doctors’ knowledge, attitudes, and practices regarding fertility preservation in cancer patients. Methods This cross-sectional study, conducted between April 2023 and March 2024, surveyed 351 General and Family Medicine doctors from the Portuguese Northern Regional Health Administration. The questionnaire, consisting of 15 questions, assessed sociodemographic profiles, knowledge, attitudes, and practices. Data were analyzed using descriptive statistics and multivariate logistic regression. Results Most participants were female (80.5%) and under 40 years old. The majority (91.5%) had treated fewer than 10 cancer patients under 40 in the past two years. Key barriers included lack of knowledge (63.3%), time constraints (57.0%), and patient age (18.5%). Male physicians were more likely to address specific fertility concerns (OR 2.239) and less likely to view patient age as a barrier (OR 0.459). Physicians aged 31-35 were less likely to discuss fertility preservation (OR 0.553) but more likely to address it in the first consultation (OR 2.969). Urban-based physicians were less likely to discuss fertility preservation (OR 2.099). Only 9.1% always discussed fertility preservation before treatment, 27.6% did so sometimes, and 63.3% never discussed it. Conclusions There are significant gaps in the knowledge and practices of family doctors regarding fertility preservation for cancer patients. Targeted training and resources are urgently needed to support family doctors in effectively discussing fertility preservation, crucial for improving the quality of life of young cancer patients wishing to preserve their fertility. Key messages • Empowering Portuguese family doctors to address fertility concerns in cancer patients contributes to comprehensive oncofertility care, improving patient outcomes and quality of life. • Integrating oncofertility support with Portuguese family doctors strengthens primary care, ensuring discussion of fertility preservation is considered as part of cancer treatment planning.