BACKGROUND Complement activation is recognized as an important factor in the progression of liver damage caused by acetaminophen (APAP). However, the role of the complement inhibitor C2-FH in APAP-induced liver injury remains unclear. AIM To explore C2-FH in protecting against APAP-induced liver injury by inhibiting complement activation. METHODS A model of APAP-induced liver injury was used to study the protective effect of C2-FH on liver injury. C2-FH was administered through intraperitoneal injection 30 minutes after APAP treatment. We detected the effects of C2-FH on liver function, inflammatory response and complement activation. Additionally, RNA-sequencing (RNA-Seq) analysis was conducted to understand the mechanism through which C2-FH provides protection against APAP-induced liver injury. RESULTS C2-FH inhibited the increase in serum alanine aminotransferase activity, aspartate aminotransferase activity and lactate dehydrogenase, and reduced liver tissue necrosis caused by APAP. Moreover, it attenuated the inflammatory response and inhibited complement activation in APAP-induced liver injury. RNA-Seq analysis provided additional explanations for the protective role of C2-FH against APAP-induced liver injury. CONCLUSION C2-FH attenuates APAP-induced liver injury by inhibiting complement activation.