In the last decades, application of synthetic toxins for control of weeds, pests and plant disease caused serious environmental problems. Allelopathy is regarded as a natural strategy in plants protecting them against environmental enemies and competing plants. This process involve plant secondary metabolites that suppress the growth and development of surrounding biological systems and named as allelochemicals. Thus, allelopathy interactions between plants and other organisms may become an alternative to synthetic herbicides and other pesticides. Coumarins are known as a large group of plant secondary metabolites mainly originated from shikimic acid pathway. This compounds are widely distributed in the Apiaceae, Rutaceae, Asteraceae and Fabaceae families of plants. Up to now, there has been many reports on phytotoxic, fungitoxic, insecticide, antibacterial and nematocidal activity of different coumarins. This reports demonstrated that some coumarins like imperatorin and psoralen exhibited considerable allochemical potential. Therefore, this compounds could be utilized to generate a new generation of bioherbicides and other pesticide chemicals that are more ecologically friendly.