Continuous growth of human population and industrialization has increased the energy demands all over the world and this has resulted in a number of energy related challenges including depletion of fossil fuels, environmental pollution, and shortage of electricity supply. These challenges made it imperative to develop and maximize the abundant renewable energy resources, particularly the biomass via upgrading thermochemical conversion routes such as co-pyrolysis. This review paper presents an overview of previous studies, recent advances, and future directions on co-pyrolysis of biomass and waste plastics for high-grade biofuel production particularly in China and elsewhere worldwide. This paper also discussed the advantages of the co-pyrolysis process, co-pyrolysis product yields, co-pyrolysis mechanisms of biomass with plastics, and synergistic effects between them during co-pyrolysis, as well as the effects of some operating parameters especially the biomass mixing ratio and pyrolysis temperature on co-pyrolysis yields. The result of this critical review showed that co-pyrolysis of biomass with waste plastics is more beneficial than the normal biomass pyrolysis alone, and that it is also a simple, effective, and optional solution to increase the energy security of a nation, achieve effective waste management, and reduce dependency on fossil fuels.