Breastfeeding rates in Mexico are among the lowest in Latin America with 14.4% for Exclusive Breastfeeding (EBF) under six months of age. It has been reported that rates has been decreasing among low-income and vulnerable population, where there is lack of healthcare assistance. Culturally appropriate counseling based on formative research has shown to be effective in improving breastfeeding. Our objective was to evaluate the effect of interpersonal counseling on EBF in a primary healthcare center in Tijuana, México. MethodsThis was a randomized controlled trial pilot with a sample of mothers with infants under 4 months of age from a Primary Care Center. Participants were randomized to a 1) Control Group, receiving counseling about immunizations as well as routine infant feeding information, and 2) Intervention Group, receiving breastfeeding counseling based on previous formative research using a socio-ecological framework. Changes in breastfeeding attitudes, self-efficacy and EBF at 2 months post-intervention were evaluated.ResultsEighty mothers were included in the study (40 in each group). The mean age was 26.4 years for mothers and 1.4 months for infants. Breastfeeding obstacles reported were breastfeeding in public discomfort (23%), infant unsatisfied (23%), pain (19%), insufficient milk (15%) and returning to work (8%). We observed a significant improvement in breastfeeding attitudes (P=0.0001), self-efficacy (P=0.018) and EBF (P=0.001). There was a 30% increase in EBF in the intervention group and 15% decrease in the control group post-intervention.ConclusionsBreastfeeding counseling based on formative research improved breastfeeding attitudes, self-efficacy and practices in this population. Breastfeeding should be promoted by well-trained health professionals with knowledge and skills to clearly communicate breastfeeding messages, and sensitivity to address women’s needs according to their sociocultural context. Since breastfeeding responds to health systems and socio-economic and cultural environments in which the mother lives; development and evaluation of programs to increase breastfeeding rates in low- and middle-income countries are necessary. Trial Registration ANZCTR ID: 380462 (Under review). Retrospectively registered.