Background and Aim: The present study aimed to investigate the effect of different nocturnal sleep patterns on shooting accuracy, reaction time, and cognitive function in military college students. Methods: The study was conducted on 48 students of Air Defense Officer University in Tehran (age,20. 7 ±,1. 15). Subjects were randomly divided into four groups: guarding post 1 (6-8, 12-14, 18-20, and 24-2), guarding post 2 (8-10, 14-16, 20-24, 2-4), guarding post 3 (10-12, 16-18, 22-24, 4-6), and control (no guarding post). After the end of the last guarding post, cognitive function (Stroop test),accuracy of shooting (10-meter air pistol shooting),simple, and choice-reaction time (Deary-Liewald test) were assessed in all groups. Data were analyzed using oneway analysis of variance (ANOVA) and Tukey or Dunnet-3 post hoc tests. Results: The results showed that compared to the control group, the shooting accuracy was significantly reduced in the subjects of the guarding post 1 (P = 0. 002) and guarding post 2 (P = 0. 001) groups. Moreover, compared to the control group, the guarding post 2 (P = 0. 001) and the guarding post 3 (P = 0. 001) groups, had poorer performance in the simple reaction test. Additionally, subjects in the guarding post 2 group had poorer performance in choice-reaction time and cognitive function compared to the control group (P = 0. 001). Conclusion: The nocturnal sleep pattern has a significant effect on cognitive function, reaction time, and shooting accuracy of military forces, particularly sleep deprivation caused by guarding post 2 has the most deleterious effect on these variables. Hence, it seems that more attention should be given to the rest after guarding post 2 in the military forces to achieve optimal performance.