This chapter attempts to systematize the myriad aspects of the effects of ionizing radiations (IR) on biological systems and their possible prevention by phytochemicals, popularly known as natural radioprotectants. To this end, the nature of radiations, their physico-chemical action on cells, and cellular effects have been discussed. The cellular effects are dealt with in terms of general, genetic and kinetic consequences of IR and organ sensitivity. Subsequently, the importance of natural radioprotective agents has been presented highlighting their areas of application, mechanism of action, sources and chemical classifications. Finally, some useful conclusions and the future prospects in the area of natural radioprotectors are briefly touched upon.