BACKGROUND: Medical emergency teams (METs) have shown their merit in preventing unexpected cardiac arrest. However, it might be impractical for small- or medium-sized hospitals to operate an MET due to limited manpower and resources. In this study, we sought to evaluate the feasibility of a medical alert system (MAS) that alerts all doctors involved in patient care of patient deterioration via text message using smart-phones. METHODS: The MAS was test-operated from July 2015 to September 2015, in five general wards with a high incidence of cardiac arrest. The number of cardiac arrests was compared to that of 2014. The indication for activation of MAS was decided by the intensive care unit committee of the institution, which examined previous reports on MET. RESULTS: During the three-month study period, 2,322 patients were admitted to the participating wards. In all, MAS activation occurred in 9 patients (0.39%). After activation, 7 patients were admitted to the intensive care unit. Two patients (0.09%) experienced cardiac arrest. Of 13,129 patients admitted to the ward in 2014, there were 50 cases (0.38%) of cardiac arrest (p = 0.009). CONCLUSIONS: It is feasible to use MAS to prevent unexpected cardiac arrest in a general ward.