Biomass co-firing with coal can help to reduce greenhouse gas emissions and can act as a low-cost stepping-stone for developing biomass supply infrastructures. This paper presents a techno-economic assessment of the biomass co-firing potential in coal-fired boilers in Czech Republic, France, Germany and Poland. The current coal power plant infrastructure is characterized by means of geographic location of the coal power plants, installed boiler capacity, type of boiler technology and year of commissioning, as extracted from the Chalmers Power Plant Database. The assessment considers type of boiler technology, type of biomass, co-firing fraction, implementation costs, breakeven prices for co-firing and an alkali index to determine the risk of high-temperature corrosion. The main factors affecting the co-firing potential are the biomass price, carbon price and alkali index. Results indicate that the total co-firing potential in the four countries is around 16 TWh year⁻¹, with the largest potential from a conversion perspective in Germany, followed by Poland. Biomass co-firing with coal is estimated to be competitive at biomass prices below 13 € MWh_input⁻¹ when the carbon price is 20 € t⁻¹ CO₂. On average, 1 TWh of electricity from biomass co-firing substitutes 0.9 Mt of fossil CO₂ emissions.