Mitomycin C (MMC) is a potent antitumor agent used against many cancers. It has a clastogenic and aneugenic effects. The protective effect of pre- and post- addition of Spirulina platensis (Sp) to the diet on MMC induced genotoxic effect and histopathological changes were evaluated in Erlich Acites Carcinoma Cell (EAC) bearing mature female Swiss albino mice. The sixty EAC bearing female albino mice weighted 30-40 gm were observed along the experimental period and classified into six equal groups. The first kept as negative control fed on Sp powder free diet. the second kept as control positive fed on Sp powder 1% in their diet 3 weeks before tumor induction (Sp1), the third group fed on Sp powder 1% 3 weeks  pre and one week  post – tumor induction (Sp1+Sp2), while the fourth group intraperitonealy (i.p) injected with MMC (1mg/kg b.wt) on the third day post tumor induction and for 7 consecutive days, while the fifth group fed on Sp1 in diet for 24 days before MMC injection  (Sp1+MMC) and the six group fed on Sp1 for 24 days pre- and 7 days post MMC injection  (Sp1+MMC+Sp2) as the same previous dose and manner. The end of experimental period, 7 days from MMC injection, 3 animals from each group were sacrificed after 90 minutes from I.M injection of colchicine. MMC exhibited a significant increase in the frequency of micronucleated (MN) erythrocytes concomitant with several chromosomal aberrations and multiple histopathological changes in the bone marrow, liver and kidney. Pre- and post- treatment with Sp showed potent anticlastogenic effect, regeneration of liver and kidney with restoration of bone marrow to the normal state. It can be concluded that Sp can minimize and mitigate the side effects of MMC on the normal cells and tissues of the body, so it can be pre- or post- treatment with MMC chemotherapy.