Objective To verify whether there is an association between the Modified Early Warning Score before the transfer from the emergency room to the ward and death or admission to the intensive care unit within 30 days. Methods This is a historical cohort study conducted in a high-complexity hospital in southern Brazil with patients who were transferred from the emergency room to the ward between January and June 2017. The following data were collected: sociodemographic variables; comorbidities, as determined by the Charlson index; reason for hospitalization; Modified Early Warning Score at the time of transfer; admission to the intensive care unit; care by the Rapid Response Team; mortality within 30 days; and hospital mortality. Results A total of 278 patients were included in the study. Regarding the Modified Early Warning Score, patients who died within 30 days had a significantly higher score than surviving patients during this period (2.0 [1.0 - 3.0] versus 1.0 [1.0 - 2.0], respectively; p = 0.006). The areas under the receiver operating characteristic curve for death within 30 days and for ICU admission were 0.67 (0.55 - 0.80; p = 0.012) and 0.72 (0.59 - 0.84; p = 0.02), respectively, with a Modified Early Warning Score cutoff of ≥ 2. In the Cox regression, the Modified Early Warning Score was independently associated with mortality within 30 days after multivariate adjustment (hazard ratio 2.91; 95% confidence interval 1.04 - 8.13). Conclusion The Modified Early Warning Score before intrahospital transfer from the emergency room to the ward is associated with admission to the intensive care unit and death within 30 days. The Modified Early Warning Score can be an important indicator for monitoring these patients and can prompt the receiving team to take specific actions.