Disposal of waste plastics is an environmental problem that has gained attention over the years. Co-pyrolysis is a promising alternative for transforming this material into solid and liquid products with high added value. This study evaluated how heating rates and polyethylene terephthalate (PET) proportions influence the properties of char obtained by co-pyrolysis. The co-pyrolysis process was carried out using Eucalyptus spp biomass, in three proportions of PET (0, 15 and 25 %) and three heating rates (1, 3 and 5 °C min−1), at a final temperature of 450 °C. We investigated the physical, chemical, energetic and thermal properties of the char produced, which included its morphology via scanning electron microscopy (SEM). The average yield of co-pyrolytic char, under all conditions of co-pyrolysis, decreased by 5 % compared to the biomass-only pyrolytic material. In addition to yield differences, the percentage of ash decreased by about 7 % in char with PET. The produced material had a maximum heating value of 32,17 MJ kg−1 and maximum energy density of 4.7 Gcal m−3 (1.10 GJ m−3). These results show the synergistic effect between PET and biomass, pointing to improvements in char generated through co-pyrolysis. The addition of PET in the process, in all conditions investigated, contributed to potentiating the energy characteristics of the material. This co-pyrolysis process can be an alternative for generation and biofuels. The co-pyrolysis of biomass and polyethylene terephthalate is a promising strategy for generating energy products and ensuring the reuse of plastic materials.