Abstract: A study on the effect of low- protein diet on the toxicity of acute doses of Actellic-20 in the heart and brain of albino rats was carried out. Three weeks old weaning albino rats Rattus norvegicus were grouped into two and fed low and normal protein diet for four weeks after which they were given Actellic-20 at low dose levels (100ppm and 150ppm) by oral intubation. The rats were sacrificed at 24h, 72h, and 120h after dosing and the activities of Alkaline phosphatase, Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) were monitored in these tissues. The activities of Alkaline phosphatase, Alanine aminotransferase and Aspartate aminotransferase were significantly reduced (P<0.05) at 24h and 120h but significantly increased at 72h in both animals fed low protein and normal protein diet dosed with Actellic-20 when compared with the control rats. It is considered that effect of this pesticide Actellic-20 on the activities of these enzymes on the heart and brain may affect energy production and amino acid metabolism in these organs.