Like his contemporaries Fernando Amorsolo and Vicente Manansala, Dumlao began his career in the 1930's. He was labeled a figurativist but was generally considered by art patrons as a muralist, a portrait painter, and a stained glass artist. He became the Art Director of San Miguel Corporation where Don Andres Soriano became his patron and introduced him to his circle of friends like Carlos Palanca and Don Manuel Elizalde, then the owner of Philippine Air Lines. Through PAL, he travelled extensively and absorbed foreign cultures and met people in high places in America and Europe. In 1960, he was tasked to repair and restore Juan Luna's "Spoliarium".