The scope of this research is to characterize and optimize the vibration-assisted ball burnishing of additively manufactured 18% Nickel Maraging steel for tooling applications. We evaluate the suitability of vibration-assisted ball burnishing as an alternative method to post-process additively manufactured tool steel. To do so, we assessed a single pass post-processing technique to enhance surface roughness, surface micro-hardness, and residual stress state. Results show that ultrasonic burnishing after age hardening functionalizes additively manufactured surfaces for tooling applications creating a beneficial compressive residual stress state on the surface. The surface micro-hardness (HV1) varied between 503 and 630 HV1, and the average surface roughness (Ra) varied between 1.31 and 0.14 µm, depending on process parameters with a maximum productivity rate of 41.66 cm2/min making it an alternative approach to functionalize additively manufactured tool components.