Organophosphate pesticides are the ester forms of phosphoric acid usually considered as secure for agriculture uses due to their relatively fast degradation rates. Organophosphorus pesticides have been extensively used in the area of agriculture to manage insect or pests of a number of economically important crops. Organophosphate pesticides are well-known as the inhibitor of acetylcholinesterase activity, not in insects only, but can also affect the nervous system of other organisms as well as humans. Organophosphorus pesticides are not restricted to anticholinesterase action, but comprise genotoxicity and teratogenicity. Such severe health consequences signify a requirement for a better understanding of the fate of organophosphates in the environment. The safe and effective use of pesticides requires knowledge of their mode of action in pests and adverse effects in non-target organisms coupled with an understanding of their metabolic activation and detoxification. Keeping all these things in mind, this review has been written on organophosphorus pesticide’s mechanistic pathway and chemistry aspects of toxicity and decomposition pathways during decomposition under different conditions.