Biomedical informatics (BMI) competencies are recognized as core requirements for the healthcare professional, but the amount of BMI educational interventions in the curricula of medical schools is limited. UNAM Faculty of Medicine in Mexico is a large public medical school, with more than 7000 undergraduate students. The undergraduate program recently underwent a major curricular revision, which includes BMI education. Two one-semester BMI courses (BMI-1 and BMI-2) were designed, with a blended-learning educational model. A department of BMI was created, with budget, offices and personnel. The first class of 1199 students started the course in 2010, with 32 groups of 40 students each. BMI-1 includes core conceptual notions of informatics applied to medicine (medical databases, electronic health record, telemedicine, among other topics), and BMI-2 embodies medical decision making and clinical reasoning. The program had a positive evaluation by students and teachers. BMI can be successfully incorporated in a large-scale medical school program in a developing country, using a blended-learning model and organizational change strategies.