A techno-economic assessment was made for thirteen large off-grid islands in the Philippines using HOMER Pro (Hybrid Optimization Model for Electric Renewables Software) to determine the feasibility of integrating waste biomass into their energy systems. Sensitivity analysis on the diesel fuel prices and biomass feedstock prices was performed to determine their effects on the levelized cost of electricity (LCOE) and the renewable energy (RE) share. The results suggest that an average LCOE reduction of around 4.57 %, fuel reduction of 5.71 %, and RE share increase of 4.99 % can be realized by integrating biomass to the existing diesel system even without incorporation of other renewable energy generators such as solar photovoltaics. In cases where biomass is available in large quantities, and the energy demand is relatively low, LCOE reduction, fuel reduction, and RE share increase may even reach up to more than 20 %. This makes the integrated biomass-diesel hybrid system a viable option for reducing diesel consumption in the off-grid islands. And even with the establishment of a feedstock market, the biomass-diesel hybrid system still has a lower LCOE compared to the existing diesel-only systems. This work provides the first systematic techno-economic study on the potential of incorporating waste biomass in off-grid islands.