Abstract The present study has dealt with characterization and co–pyrolysis of binary and ternary blends of three biomass, viz. water hyacinth (WH), Thevetia peruviana (TP) and sugarcane bagasse (SCB). The biomass blends were characterized for proximate and ultimate analysis, surface morphology and functional groups. Co–pyrolysis of blends was carried out using a thermogravimetric analyzer (TGA) at heating rates of 8, 10, 15 and 30 °C min−1. TGA data was analysed using Ozawa–Flynn–Wall (OFW), advanced isoconversional model of Vyazovkin (Vyazovkin _AIC) and distributed activation energy model (DAEM). The dominant reaction mechanism of co–pyrolysis at different stages of conversions was deduced using Criado plots. The kinetic parameters of activation energy and pre–exponential factor, and thermodynamic parameters of ΔH and ΔS showed large variation with conversion, which is indicative of complex chemistry of thermal conversion of various structural components of biomass with synergistic interactions. The activation energies for binary blends WH SCB, WH TP, TP SCB were in the range 122.90–237.53, 127.93–272.92, and 124.80–235.94 kJ mol−1, respectively. For ternary blends WH 111, WH 211 and WH 311, activation energy varied in the range 119.64–194.31, 123.40–246.80, and 121.65–194.75 kJ mol−1, respectively. The predominant reaction mechanism for all blends was ordered reaction (F1) in lower conversion range (α ≤ 0.25), and diffusion limited process (D1 or D2 or D3) in higher conversion range (α = 0.35–0.55). Positive ΔH for all blends indicated endothermic nature, while positive ΔS indicated more disordered system after reaction – typical of pyrolysis.