Purpose: This study was conducted to investigate the effect of direct verbal feedback from an expert during endotracheal intubation skills training using a mannequin compared to practice alone without feedback. Methods: 154 fourth-year medical students at the Pusan National University were divided into control or feedback groups. Both groups were taught by experts using a mannequin at a clinical skills learning center. The feedback group (n=66) received verbal feedback from the expert throughout training. Skills acquisition was tested during a Clinical Performance Examination. Results: There were no differences between the control and feedback groups in terms of prior experiences with endotracheal intubation, confidence level to perform the skill, and grades received from previous clinical clerkships. The average score of the feedback group was significantly higher than that of the control group (14.06 versus 11.98, p<0.05). When the students were divided into ‘exceeds expectations’, ‘meets expectations’ and ‘needs development’ groups according to a global rating, more students from the feedback group were in the ‘exceeds expectations’ group and less were in the ‘needs development’ group compared to the control group (p<0.05). The results showed no significant relation with training date. Conclusion: This study demonstrated that direct verbal feedback from an expert during training significantly improves the performance of endotracheal intubation skill. Feedback acts as an essential component of clinical education; and its effect is prominent, especially in students who require further development.