Irinotecan-based regimens are commonly used for treatment of colorectal cancer, which is limited by mucositis and non-alcoholic steatohepatitis (NASH). Silymarin (SIL) prevents fatty liver disease in the clinical setting and in models of liver damage induced chemically. This study investigated the possible effect of SIL on irinotecan (IRI)-induced NASH. Swiss female mice were injected with saline (SAL 5 ml/kg i.p.), IRI (50 mg/kg i.p.), SIL (150 mg/kg p.o.) or IRI (50 mg/kg i.p.) + (SIL 1.5, 15 or 150 mg/kg p.o.) thrice/week/7 weeks. On the seventh week, blood samples were collected for transaminases assay and livers were collected for histopathology, measurement of the total lipids, malondyadehyde (MDA), non-protein sulfhydryl groups (NPSH), cytokines (IL-1β, IL 6 and IL-10), 3-nitrotyrosine (N-Tyr) and toll-like receptor 4 (TLR4) immunoexpression, quantification of NF-kB, α-smooth muscle actin (α-SMA), and Escherichia coli 16S rRNA gene (RRS) expression. IRI increased liver transaminases, neutrophil infiltration, lipid accumulation, MDA, IL-1β and IL-6 levels, N-Tyr and TLR4 immunostaining, NF-kB, α-SMA expression and RRS versus the SAL group (p < 0.05). Additionally, SIL (1.5 mg/kg) improved these parameters (p < 0.05), except neutrophil infiltration and RSS versus the IRI group. Furthermore, the SIL (15 mg/kg) only improved the inflammatory parameters, the expression of α-SMA and RRS versus the IRI group (p < 0.05). The higher dose of SIL (150 mg/kg) was even more deleterious than the intermediate dose. Therefore, silymarin showed a dual effect on liver damage induced by IRI. Hepatoprotection seems to involve the inhibition of oxidative stress and protein nitrosylation, preventing activation of hepatic fibrosis mechanisms.