The environmental, social, and economic concerns regarding fossil fuels necessitate the demand for an efficient energy mix utilising renewable resources like biomass for sustainable development. Recent interest in the thermochemical conversion of coal and biomass into bioenergy via co-pyrolysis processes is gaining importance. This review critically assesses the behaviour of different types of coal and biomass blends during co-pyrolysis from various perspectives, including the effects of temperature, blending ratios, heating rate, synergistic and inhibitive behaviours, heat transfer mechanisms, nature of products, and their future applications. The possible synergies arising due to differences in the compositions of coal and biomass are discussed. In addition, the synergistic effect on co-pyrolysis yield is critically presented. Moreover, it is analysed that the co-pyrolysis offers higher yields of liquid and gaseous fuels compared to individual feedstock coal and biomass. Co-pyrolysis of coal and biomass can be promoted from a scientific standpoint; however, further research is still required for the integration of new technologies to enhance the effectiveness of co-pyrolysis.