This study investigated the effects of Rapid Eye Movement (REM) sleep deprivation on Pain Perception levels using the chemical method and the thermal method of pain assessment. Twenty four male wistar rats were used in this study. Twelve of them were deprived of REM sleep using the method described by Jouvet and others in 1964 and later modified by Harry and others in 1965. The control were however not deprived of any type of sleep but were subjected to normal physiological conditions in the animal house. The experimental animals were deprived of REM sleep for four days, after which their pain perception levels were tested using the formalin test and the tail flick tests. The result of the pain perception tests in experimental groups after the REM sleep deprivation when compared with the control showed a significant increase (p<0.05) in the latent periods in the thermal model and a significant decrease (p<0.05) in both phases of the formalin chemical model. In conclusion, sleep deprivation can lead to decrease in pain perception and this may be as a result of alteration of the serotonin level in the body which serve as a mediator for both pain and sleep.