The antifeedant and anthelmintic activities of crude extracts of the shells of Anacardium occidentale were studied by comparing it's activity with the activity of Azadirachta indica A Juss (Kernel), a commercial standard. The test extracts of A. occidentale in petroleum ether, dichloromethane: methanol showed better activities compared to A. Indica. To Study the anthelmintic activity, the addition of piperine to the formulation significantly enhances the activity. The phytochemical investigation of test extracts showed the presence of phenols namely cordol, cardanol and anacardic acid by TLC studies. The most potent extracts are non toxic to mice.