Background:The practice of anesthesia requires good awareness, parallel decision-making and fine motor skills. The duration of working hours of anesthesiology residents is often more than 12 hours.Objectives:This study aimed to measure cognitive and psychomotor functions of anesthesiology residents after 12 working hours.Patients and Methods:This was an observational study on anesthesiology residents who underwent 12 working hours. Each subject, who fulfilled inclusion and exclusion criteria, had their cognitive and psychomotor functions tested at 0 and 12 hours. The cognitive function was measured by “Cognitive Stimulation” test, while the psychomotor function was measured by the grooved pegboard. Statistical analysis was conducted to compare the results between 0 and 12 hours.Results:Cognitive Stimulation” test revealed statistically significant decrease at sequential image frequency stimulation (P = 0.035). Other stimulation tests did not show any statistically significant result. Grooved pegboard test showed statistically significant decrease in psychomotor function from 0 to 12 hours (P = 0.037).Conclusions:There was a decrease in cognitive function, including attention, visual memory, naming, and executive function, as well as psychomotor function among residents of Department of Anesthesiology and Intensive Care, Faculty of Medicine, Universitas Indonesia, who underwent 12 working hours.