Objective: Extensive use of pesticides has harmful effects; they can damage human health as well as the environment. Abamectin (ABM) has been widely employed and is one of the most commonly used pesticides in Algeria. Methods: To evaluate the toxic effects of ABM, twenty-eight male and female rats ( Rattus norvegicus ) were randomly assigned to four groups. Groups 1 and 3 were the male and female control groups, respectively, which received distilled water. The experimental male and female groups, 2 and 4, received 2.13 mg/animal/day of abamectin, administered orally over 28 days. The animals were maintained in the same conditions without treatment for 14 days after this period. Plasma samples at 14, 28 and 42 days were used to determine biochemical parameters and avermectin B1a residues in rat plasma. Quantities of B1a in the liver were evaluated at the end of the experiment (day 42). In this study a UHPLC–MS/MS method was used to determine B1a residues in the plasma and liver. Results: Abamectin caused an increase ( p γ -Gt in male and female rats at 14, 28 and 42 days. All experimental animals showed the time-dependent presence of B1a residues in the plasma samples at 14 and 28 days but, after 42 days, there were no residues in the plasma of ABM-treated rats. B1a residues in the liver were detected in male and female experimental rats at the end of the experiment. Abamectin caused histopathological damage of the liver tissues in the form of dilated veins, leucocyte infiltration and degenerative hepatocytes. Conclusion: Our results show that ABM perturbs liver function in the rat.