Disruption in feedstock supply due to seasonal availability, and logistics problem poses a threat to smooth biomass gasification. To mitigate this problem, co-gasification of different biomass feedstocks may be a reliable and efficient means of syngas production. Furthermore, the oil palm trunk (OPT) has been neglected in conducting thermochemical studies due to its high moisture and nature of availability compared to oil palm frond (OPF), despite its abundance during replanting periods and remarkable thermochemical properties. Hence scarce information is known on its gasification and co-gasification studies. In this study, OPT and OPF were co-gasified using a lab scale downdraft gasifier, to evaluate the influence of blending ratio on co-gasification performance and syngas quality at a temperature of 800°C, particle size of 5-10 mm, and an airflow rate of 2.5 L/min. The blends utilised were OPT/OPF at ratios 30/70, 50/50 and 70/30 for co-gasification, whereas pure OPT and OPF were used for gasification. The optimum blend was 30OPT/70OPF, as it produced the highest gas constituents of CO, H2 and CH4, compared to the other blends. It also produced the highest gas yield and heating value, 1.47 Nm3/kg and 6.85 MJ/Nm3, respectively. Its co-gasification efficiencies were also higher for both cold gas (56.35) and carbon conversion (68.53). In the gasification study, OPT was 7 higher than OPF in H2 yield, whereas OPF was higher in CO yield by 20, and in terms of CH4 both yielded almost same results. The gas yield and heating values of syngas produced in OPT and OPF gasification were comparable as the difference in both cases was not more than 5. It is deduced that there exists positive synergistic effect in 30 OPT/70 OPF blend as evident from the results obtained, and that OPT is a capable gasification fuel that can complement OPF in case of supply shortage. © 2020 John Wiley & Sons Ltd