To analyze the key successful factors of a national educational strategy for early breast cancer detection developed in Mexico for primary health care personnel from 2008 to 2014, an educational strategy to train physicians, nurses, health promoters, and medical students from local ministries of health with a competency-based approach was developed and implemented using diverse educational modalities, face-to-face, blended, and a massive open online course (MOOC). Formative and summative evaluations were used during the implementation of the course. A total of 19,563 health professionals were trained from 2008 to 2014. The graduation rate, an average of all educational modalities, was 91 %, much higher than those previously reported in the literature. The factors that might have influenced this success were (1) the training strategy, which was designed according to the characteristics and specific needs of the target groups; (2) the political will and commitment of the country's health authorities; (3) the technological and educational models used; and (4) the punctual follow-up of participants. This study shows that carefully designed educational interventions can improve service professionals' competencies and that regardless of the modality, face-to-face, blended learning, or MOOC, high graduation rates can be achieved. Further evaluation is required to demonstrate that the competencies remained in all target groups after 6 months of the intervention and that the women served by the trained personnel were provided accurate information and timely diagnoses of breast cancer.