Strengthening healthcare systems requires evidence-based health education strategies that promote preventive behaviours and civic engagement. This study aimed to enhance healthcare awareness and reinforce university–school partnerships between Spain and Brazil through a collaborative project with the Blood Donors’ Brotherhood, focused on promoting voluntary blood donation as a public health priority. Implemented via the Research and Excellence High School's Program, the initiative utilised Service-Learning (SL) and Project-Based Learning (PBL) methodologies to create an impactful health educational intervention. The effectiveness of the intervention was evaluated through a quasi-experimental study involving 228 responses from individuals aged 17 to 51 years (M = 24.12, SD = 7.75). Participants were divided into experimental and control groups, including high school and university students in health and education programmes. The intervention was assessed pre- and post-implementation using a survey based on the Blood Donation Knowledge Questionnaire (BDKQ-Brazil), whose Spanish translation (BDKQ24-Spain) was validated through Factor Analysis. The two-factor BDKQ22-Spain model showed strong reliability (KR-20 = 0.85), supporting its suitability for measuring this construct. The study revealed that minors, future teachers, and therapists had less knowledge about blood donation compared to nursing students. However, post-intervention results showed significant knowledge improvements, reaching levels comparable to those of nursing students. This innovative project demonstrates that university–school partnerships strengthen health education outcomes related to blood donation and promote health promotion, contributing to sustainable healthcare systems, social responsibility, and the overall well-being of diverse student populations.