Pesticides or their metabolites may have the capacity to disturb and hinder the functions of some essential organs including spleen. This study examined side effects of propanil on the spleen of mice. Experimental groups were exposed to propanil through oral administration for 30 consecutive days. The separation of capsule from the splenic parenchyma, a thickening of the capsule, congestion in the splenic parenchyma, dilated sinusoids, and arteriolar enlargement, karyolysis in megakaryocytes and amyloid formation were determined in the low-dose group. Hemorrhage and separation in the capsule, amorphous megakaryocytes, karyolysis in megakaryocytes, congestion in the splenic tissue and sinusoidal enlargement, fibrosis, lobule formation, enlargement of the white pulp and deformation of arteriole were detected in the medium-dose group. Hemorrhage in separated capsule, karyolysis in megakaryocytes, congestion in the splenic parenchyma, enlargement of the white pulp, fibrosis, necrosis in the white pulp, congestion in the enlarged sinusoid and cellular swelling in the splenic red pulp were observed in the high-dose group. These findings clearly demonstrated that propanil induced important dose-related histopathological damages. Based on our results, we can clearly say that it may have the capacity to cause this organ’ failure.