Background: Prolonged resident duty hours may affect patient care. There are no restrictions to the amount of hours a resident can work which may lead to medical errors and lapses in patient care. Aims and Objectives: The purpose of this study was to prospectively evaluate the effect of sleep deprivation (SD) on finger dexterity at different intervals of SD during the residents' on-call period and to identify the duration after which these effects begin. We further tested if this decline correlated with the subjective assessment of sleepiness. Materials and Methods: The finger dexterity was measured by the O'Connor dexterity apparatus, and subjective sleepiness assessment was carried out using pictorial sleepiness scale in 30 resident doctors at 6 h intervals during their on-call period which lasted for 24 h. Results: The finger dexterity was significantly decreased at the end of the 24 h duty period as compared to the baseline. This deterioration began after being on-call for 12 h and progressed thereafter. The changes in finger dexterity correlated negatively with the subjective sleepiness assessment. Conclusion: 24 h of SD during on-call duty significantly decreases the finger dexterity in resident doctors. This might be a major cause of medical errors and hamper patient safety.