The use of 3D printing technology for manufacturing construction materials is gaining popularity, however, only a few studies have reported the fire behavior of such parts. In this research, the fire properties of 3D printed polylactide acid (PLA) parts with varying infill densities along with the tensile properties were analysed. The results from the fire tests showed that increasing the infill density increased the fuel load, which sustained combustion. Hence, the peak heat release rate and total heat release increased with an increment in infill density percentage. It was also observed that the increasing infill density had no effect on the flammability rating of the parts due to the constant shell thickness used for all the parts. In addition, the tensile strength and ductility of the parts increased with density as a porous part is more susceptible to failure than a solid homogeneous part.