Yoyo cleanser bitters, a polyherbal drug is widely used by Nigerians with the purpose of purifying the entire system of the body. This study was aimed at determining the effect of the drug on the morphology of the cerebellum of wistar rats. 16 rats divided into four groups; a control group, an Low dose of 0.05 ml group, a normal dose of 0.10 ml group and an High dose of 0.20 ml group. The weight of the wistar rats was between 150 – 230 g. The rats were fed and administered these amounts of drugs daily with their weights recorded after one day interval for 2 weeks. The result of the weights of the animals, and cerebellum of each of the experimental groups does not reveal any significant effect morphologically. The plates picked at random for all the groups revealed a marked change when compared with the control. The over dose group showed that the granular layer of the cerebellar cortex is hypertrophied with a corresponding increase in granular cells. It is deduced that high consumption of yoyo cleanser bitters for long period of time will have a significant effect on the histology of the cerebellum of wistar rats which may lead to cerebellar dysfunction.