The fire-fighting chemicals (FFCs) are natural or synthetic substances increasingly used as additives for improving the fire extinguishing effectiveness of water and reducing the impacts of wildfires. Through either chemical or physical actions, the FFCs increase the ignition delay time and reduce the fire intensity, the spread of fire and the consumption of fuel, delaying also the recovery of the combustion process. Long-term FFCs are water solutions of fire retardants (usually ammonium sulphate or phosphate salts) and other chemicals to improve their application with ground or aerial equipments (thickeners, colouring agents, corrosion inhibitors and bactericides); their effectiveness mainly relies on the dose of retardant applied and remains even after the carrying water disappears. Short-term FFCs, either foams or gels, are also water solutions of different chemicals (foaming agents, wetting agents, foam stabilizers, dispersants, super-absorbents, corrosion inhibitors), but their effectivity depends mainly on their ability to increase water retention by fuels and disappears once water is evaporated or drained out. During wildfire fighting, FFCs may enter into contact with all components of the target ecosystem; therefore, care must be taken because they contain a wide variety of chemicals with potential deleterious effects on aquatic and terrestrial ecosystems, and eventually on human health after ingestion or prolonged contact. As the environmental impacts can be important, mainly due to the high N and P content of long-term FFCs and the surfactant ingredients of short-term FFCs, in the last decade increasing efforts have been undertaken to develop more environmentally friendly FFCs.