Introduction: We explore the limitations to adherence of hand-washing and evaluate the impact of a mHealth intervention for hand hygiene in residents. Methodology: We explore resident's perspectives about Hospital-acquired infections (HAI) and hand washing. In baseline, participants completed socio-demographic characteristics and hand-washing habits survey. The intervention consisted of sending SMS three times a week for two months about hand hygiene and "five moments"for hand washing. The cultures of hands and cell phones were analyzed at baseline, 2 months and 4 months. We used chi-square and adjusted Generalized Estimating Equations. Results: Five physicians were interviewed and 33 participants were included for quantitative analysis. Critical barriers that hinder hand washing were identified. The proportion of Staphylococcus aureus in hands was 54.5% at baseline and was significantly reduced at 2 months follow-up (p = 0.009), but, benefit was lost when the intervention was discontinued; Escherichia coli and Klebsiella sp. were observed in 22.2% of hands, no changes were noted with intervention. In cell phones, there was a tendency to lower values of bacterial colonization after intervention for Staphylococcus aureus growth. Conclusions: High prevalence of contamination in hands and phones in medical residents were found. Serious barriers to compliance with hand washing must be overcome. It is possible that prolonged or continuous interventions could be necessary to optimize hand washing and reduce hand and cell phones contamination.