The solidification and microstructural evolution during deposition, as well as the structural evolution during post heat treatment, determine the mechanical properties of wire-arc additively manufactured maraging stainless steels. In the present work, we tune the austenite reversion and nanoscale precipitation during post heat treat-ment and achieve an excellent combination of strength and ductility (ultimate tensile strength-1340 MPa and uniform elongation-10.5 %). The structural evolution is studied through computational thermodynamics, electron microscopy, in situ small-angle neutron scattering, and synchrotron X-ray diffraction. The as-built microstructure is composed of mainly martensite and retained austenite (-30 vol%) together with a minor fraction of delta-ferrite, M23C6, Nb(C, N), spherical and ellipsoidal Cu precipitates and some inclusions. The presence of these phases cannot be fully predicted by the Scheil-Gulliver model due to the complicated thermal history and non-homogenous elemental distribution. The reverted austenite formed during the post heat treatments has high stability and fine grain size (-1 mu m), which contributes to the excellent ductility, while the nanoscale precipi-tation hardening contributes to the achieved high strength.