Histological effects of Monosodium glutamate (MSG) commonly used as food additive on the spleen of adult Wistar rats were carefully studied. The rats (n=30), average weight of 115 gm were randomly assigned into four treatments (n=6) and control (n=6) groups. The rats in the treatment groups received 4 mg/kg IP of MSG for fourteen days, while the control group receives the same volume of distilled water intraperitoneally. The rats were sacrificed after the last day of injection (group 1) and on 14 (group 2), 28 (group 3) and 42 day (group 4) after cessation of the treatment with MSG. The spleen was carefully dissected out and quickly fixed in 10% buffered formaldehyde for routine histological study after H&E method. The histological findings after H&E methods for group 1 indicated that the treated sections of the spleen showed atrophy of the while pulp, germinate centers were missing and red pulp of the spleen showed aplasia. The treatment (Group 2) showed vacuolation of some splenic cells with decreased cellularity, and sinusoidal spaces were large. Animals of group 3 showed slight atrophy in the white pulp and aplasia of red pulp where it began to retain normal structure. In the animals sacrificed at the end of the experimental period, the spleen retained its normal structure. These findings indicate that MSG consumption may have some deleterious effects on the spleen of adult Wistar rats which is reversible and does not lead to permanent damage but the normal structure of the spleen would need a long time to be regained. It is recommended that further studies aimed at corroborating these findings be carried out.