Maraging steels are traditional ultra-high-strength structural alloys prominent in aerospace and hydrospace applications. We evaluated the structure and magnetic properties of gas-atomized maraging steel powder for additive manufacturing, over a range of temperatures, and compared with commercial magnetic alloys. We characterized the structure by a combination of methods: x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, and the magnetic properties by vibrating sample magnetometry. The powders comprised martensite along with traces of retained-austenite and other intermetallics. The powders exhibited the following magnetic behavior at ambient temperature: coercivity (Hc) ~3 kA/m, magnetic anisotropy (K1) ~1.8 x 10^6 J/m3, magnetic remanence (Mr) ~1 Am2/kg, and magnetic saturation (Ms). The Hc, K1, Mr, and Ms increased at sub-ambient temperatures. The magnetic moment per atom (µh) of the powder was estimated to be ~1.93 µB. With the increase in thermal-treatment temperature, the MS and Hc increased and decreased, respectively.