The numbers of acutely ill patients (AIP) are admitted in general hospital wards increased. The failing to identify, manage and deliver timely and optimal care to AIPs may lead to catastrophic outcomes. A qualitative study aimed to define the current state of AIPs in Iranian hospitals showed the flaws and shortcomings in the current services for identifying and managing AIPs. An evaluation study was designed to explore the potential impact of Critical Care Service (CCS) in an Iranian University Hospital. The study design was a Stepped-Wedge Cluster Randomized Controlled Trial. The study included, for each ward, an unexposed to the intervention, training, and an exposed to the intervention phase. The data was analyzed using three methods: all patients, matched randomized and before-after. The null-hypothesis was tested using the mixed effect logistic regression, linear mixed and the mixed effects models. The results showed that there are no significant differences in mortality, CPR, ICU admission and length of stay. A second qualitative to find the views of staffs toward the CCS indicated that the CCS had several favorable effects, however; overcoming contextual problems in the hospital, prior to implementation of CCS, may facilitate its implementation.