This paper investigates the effects of the horizontal projection on the spill flame ejected from an enclosure. Experiments were carried out in a reduced-scale enclosure and a horizontal projection was installed above the opening. The spill flame beneath a horizontal projection is composed of a horizontal momentum-dominated rectangle region and a buoyancy-dominated semicircle region. The overall averaged excess air ratio and the averaged entrainment coefficient of the spill flame beneath a horizontal projection were investigated. A theoretical model for the total flame length was developed. The model predictions agree well with the measured values.