Background: Modified rapid sequence intubation (RSI) is crucial in emergency surgery, particularly for patients with a full stomach, as it allows for the administration of general anesthesia (GA). Objectives: This work aimed to evaluate mivacurium effectiveness and optimal dose in modified RSI. Methods: This randomized double-blind study involved 100 patients, aged between 20 - 60 years, of both sexes, with the American Society of Anesthesiologists physical status classification of I - III, who were undergoing emergency surgery under GA. Patients were randomized into two equal groups and received mivacurium in a dose of 0.3 mg/kg in group M1 or 0.4 mg/kg in group muscarinic-2 (M2). Results: Intubating conditions were significantly better in group M2 than in group M1. The onset of adequate muscle relaxation was significantly earlier in group M2 than in group M1 (P < 0.001). At the third minute, mean arterial blood pressure recordings were significantly lower in group M2 (P = 0.04) than in group M1. The recovery time was significantly longer in group M2 than in group M1 (P < 0.001). Conclusions: Mivacurium in a 0.4 mg/kg dose resulted in more favorable intubating conditions during RSI and a more profound, earlier onset of muscle relaxation, but with a longer recovery time compared to the 0.3 mg/kg dose.