The co-pyrolysis of bamboo sawdust (BSD) and linear low-density polyethylene (LLDPE) is studied for the first time using thermogravimetric analysis (TGA) in the temperature range of 30–900 °C at heating rates 5, 10 and 20 °C·min−1. A blend containing 25 wt% BSD and 75 wt% LLDPE (BP1:3) shows the highest synergism as compared to other blends studied. The activation energy drop (36% with respect to biomass) is also highest with this blend. The kinetic parameters are determined using three models based on the isoconversional method: Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), and Friedman (FM) models. The mean values of apparent activation energy for the decomposition of blends (BP3:1 (75 wt% BSD and 25 wt% LLDPE), BP1:1 (50 wt% BSD and 50 wt% LLDPE) and BP1:3) are determined to be 357, 371 and 143 kJ mol−1 from KAS, 368, 400 and 165 kJ mol−1 from OFW and 468, 356 and 255 kJ mol−1 from FM, respectively. The reaction follows a multistep mechanism as depicted by Criado’s master plot. The decomposition of the blend BP1:3 follows a nucleation growth (A2) model in the lower conversion range and diffusion (D2) model in the higher conversion range. Display omitted •The co-pyrolysis of bamboo biomass and LLDPE is studied using thermogravimetry.•The highest synergism and an Ea drop of 36% with the blend 1:3 biomass:plastic.•Master plot: A2, and D2 mechanisms at lower and higher conversions, respectively.•The Ea for the blends 3:1, 1:1 and 1:3 are 397, 376, and 188 kJ mol−1, respectively.•The mean reactivity order of blends is found to be 1:3 > 1:1 > 3:1 at all heating rates.