The growth of the palm oil industry has resulted in an increase in the production of solid waste, created from the extraction of fresh fruit bunches, which can take the form of palm oil boiler ash (POBA). POBA can be used to modify asphalt binder and asphalt mixtures to reduce the harmful effect of this waste on the environment. The objective of each modification is to increase the strength, stiffness, durability, workability and constructability of asphalt mixtures while reducing the environmental effects. This study examines the physical and chemical properties of 60/70 penetration-grade asphalt binder, modified using POBA and warm mix asphalt (WMA) additive. Ranges of modified binder were prepared by adding 2% of the warm additive Rediset with different POBA contents (3%, 5%, 7% and 9%) throughout the wet mixing process. Physical properties of modified binder were obtained from penetration, softening point, ductility and rotational viscosity tests. Molecular components and structures of the modified binder were identified using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the thermal properties of modified asphalt binder. The addition of 7% POBA in WMA binder showed the best characteristics in the tested consistency of its physical properties. As a modifier, POBA showed no chemical interaction with the molecules and structures of the asphalt binder and did not significantly change the physicochemical transitions. From the results, it can be concluded that using POBA in WMA binder for pavement construction is a viable option.