Plants contain many bioactive compounds as a means of defense against insects. Some plants produce toxic compounds that could affect or kill the insect completely. These natural compounds are an alternate for synthetic insecticides that cause many problems to the environment and human health. Hence, there is an urgent need for botanical insecticide which is eco-friendly and control insects in short duration. The secondary metabolites namely alkaloids have significant effects on insects. The alkaloids can affect insects through biological action such as disturbing the cellular and physiological process via redox imbalance and hormonal regulation. In this review, we present data on sub lethal and lethal toxicity caused by the various species and alkaloids obtained from the plants. The pure alkaloids and extracts of various plants cause toxicity towards insects which are considered as the important point of view economically.