This study aimed to show the effect of acetamiprid, a neonicotinoid insecticide, on B-cell lymphoma 2 (Bcl-2) gene expression, which plays an important role in apoptotic mechanisms in liver tissue. The study consisted of four groups in total, in which three doses of acetamiprid (5, 10, and 15 mg kg-1) were administered, together with the negative group, in which no substance was administered. Liver tissues resected from mice sacrificed by cervical dislocation after 14 days of acetamiprid administration by gavage were fixed in a 10% formaldehyde solution for histological and immunohistochemical analyses and blocked in paraffin after routine tissue follow-up, and sections were stained with haematoxylin-eosin and immunostaining. Histological analysis revealed normal liver tissue in the control group; whereas, sinusoidal dilatation, vasodilatation, and necrosis and steatosis in the parenchyma were found in the acetamiprid-treated group at an increasing rate depending on the dose amount. The immunoreactivity of Bcl-2 in liver tissue was observed in the sinusoidal epithelium. Bcl-2 immunoreactivity was observed severely in the control and 5 mg kg-1 groups and moderately in the 10 mg kg-1 and 15 mg kg-1 acetamiprid-treated groups. Bcl-2 immunoreactivity was observed homogenously in the region from the central vein to the Kiernan’s space. It was observed that acetamiprid used in the study showed a toxic effect on liver tissue, affected bcl-2 expression, an important biomarker in apoptotic pathways, and induced a dose-dependent decrease in bcl-2 immunoreactivity.