Methotrexate (MTX) is widely used chemotherapeutic agent with different side effects including germ cells toxicities. Silibinin is one of the structural isomers of silymarin, with different phytotherapeutic applications, and its possible protective effects against MTX induced germ cells damage were investigated in this work. Twenty five male mice were divided into five groups (n=5) allocated as follows: Group 1 received buffer for five days given by single intraperitoneal (IP) injection per day; Group 2 in addition to buffer for five days, animals received at day five single dose of 20 mg/kg of MTX IP. Groups (3, 4, and 5) received respectively, (50, 100, or 150 mg/kg body weight) of silibinin IP single daily dose for five days then at day five 20 mg/kg of MTX IP. Microscopic examinations of sperms, histological examinations of testis and serum testosterone had been measured. Silibinin showed a significant decrease in the percent of dead/live sperm with significant changes in interstitial space and in the diameter of spermatide. The results indicate that silibinin can mitigate some of the toxic effects of MTX in testicular tissue.