Objective. This study aimed to investigate the effects of gallic acid and silymarin against nephrotoxicity and hepatotoxicity caused by cisplatin. Materials and Methods. In the study, 56 Wistar Albino rats were equally divided into eight groups. Group 1 was the control group; group 2 was the group receiving cisplatin; group 3 was the group receiving cisplatin + gallic acid; group 4 was the group receiving cisplatin + silymarin; group 5 was the group receiving cisplatin + silymarin + gallic acid; group 6 was the group receiving silymarin; group 7 was the group receiving gallic acid; group 8 was the group receiving gallic acid + silymarin. AST, ALT, urea, creatinine, albumin, globulin, and total protein levels were measured at the end of the study. Superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), glutathione (GSH), and 8-hydroxy-2′-deoxyguanosine (8OH-dG) levels were measured in kidney and liver tissues. Additionally, histopathological evaluations of the tissues were also performed. Results. In kidney and liver tissues, cisplatin significantly increased MDA and 8-OHdG levels compared with treatment groups (
p
<
0.05
). Silymarin-treated group significantly increased the SOD activity and GSH amount in the liver tissue compared with the cisplatin-treated group (
p
<
0.05
). Gallic acid significantly increased CAT activity compared with the cisplatin-treated group (
p
<
0.05
). It was determined that the cisplatin-treated group significantly decreased CAT and SOD activity compared with the control group (
p
>
0.05
). Gallic acid showed a significant increase in CAT and SOD activity in kidney tissue compared with the cisplatin-treated group (
p
<
0.05
). Conclusion. As a result, it was observed that gallic acid silymarin had a protective effect on cisplatin-induced nephrotoxic and hepatotoxic effects.