Laser powder bed fusion (PBF/L) is a popular metal additive manufacturing (AM) process used to manufacture complex metallic 3D components. Maraging steel is one of the metals used in AM and it belongs to the class of ultra-high-strength steels used in aerospace and tooling industries. In the PBF/L process, a laser beam is used to melt and fuse the metal powder particles. This creates a high thermal gradient and rapid cooling of the melt pool results in columnar grains. The microstructure of AM part is entirely different from the conventionally manufactured case and this necessitates post-AM heat treatments. The current paper reviews the effects of printing parameters and heat treatment on microstructure and mechanical properties of PBF/L produced maraging steel 300 alloy. Tensile, impact, fracture, and fatigue properties of as-built and heat-treated PBF/L parts are discussed in detail.