Co-pyrolysis of pinewood and different kinds of plastic wastes in different mass fractions using polypropylene (PP), polyethylene terephthalate (PETE), and polycarbonate (BPC) were investigated. The results compared with the pyrolysis of individual components revealed non-additive synergistic effects from co-pyrolysis. Differential thermography (DTG) results showed enhanced decomposition peaks of biomass along with longer evolution of syngas and decreased peak of plastic polymers using BPC or PETE. Char residue was non-additively reduced by some 5% (dry wt, basis) using PP and BPC, and by 2-3% using PETE when pyrolyzed with biomass. This suggests increased carbon conversion efficiency and volatiles yield during co-pyrolysis compared to individual component pyrolysis. First order distributed activation energy modeling (DAEM) with 5 pseudo-components revealed that the synergistic effects of biomass with PP or PETE were mainly due to physical nature of the polymers as observed from increased activation energy bandwidth of biomass decomposition. BPC and pinewood mixtures showed an overlap in their activation energy distribution between 100 and 150 kJ/mol. This overlap caused the set of reaction with similar energetics to mutually interact chemically and enhance the composite mixture pyrolysis. Activation energy of BPC in the presence of pinewood was reduced by some 50 kJ/mol compared to individually examined polymer decomposition. The observed quantitative synergistic kinetics results in co-pyrolysis of biomass-plastic wastes mixtures as compared to individual component pyrolysis provide vital information towards the development of feed-flexible, clean pyrolysis and gasification system for efficient fuels production.