Intumescent fire-retardant coating is a passive type of protection against fire, design to reduce the heat transfer from the source of fire to the steel substrate in a duration of time.This research investigates the effect of Magnesium Oxide as a filler in expandable graphite-based intumescent fire-retardant coatings.The coating was developed by varying weight percentage (0.5�2.5wt) of magnesium oxide towards binder in the coating in addition to ammonium polyphosphate, melamine, boric acid, zinc borate, and expandable graphite.The samples were subjected to fire tests to investigate their performance.The heat shielding fire test shows a decrease of back substrate temperature when increasing the amount of magnesium oxide in the formulation up to 242 � for 1 h.The samples were subjected to a fire control test to investigate the intumescent factor (IF) at 600 � for 1 h in a carbolite furnace.MG1.5 shown the highest with the expansion of 8.33 Intumescent factor.Thermal gravimetric analysis, water immersion, and adhesion tests were also performed to study the sample's thermal stability and adhesion strength towards the substrate.The result showed that adding magnesium oxide in the formulation of intumescent coating improved the coating's thermal performance, thus increasing the protection time of steel substrate. © 2023, Institute of Technology PETRONAS Sdn Bhd.