Two advanced additive manufacturing (AM) technologies based on laser powder bed fusion (L-PBF) and wire-arc additive manufacturing (WAAM) were implemented for the building of nickel-aluminum bronze (NAB) alloy that has potential applications in the marine industry. The significantly altered microstructural features were characterized concerning the grain boundary character distribution and the phase structure. For the deposited NAB alloys using these two different strategies, due to the different intrinsic cooling rates controlling the layer-upon-layer melting and solidification mechanisms, different microstructure characteristics were obtained. Consequently, the diffusion of tracer elements through these two variant additively manufactured structures were studied in correlation with their microstructural aspects. As the leading outcome of this study, so-called “non-equilibrium” βʹ boundaries were observed in the martensitic structure of the L-PBF manufactured alloy with an irregular solid solution of elements and local non-equilibrium phase transformations resulting in promising altered diffusion rates with transformed mechanisms and consequently with different activation energies for grain boundary diffusion. While, in the case of WAAM-produced alloy, the equilibrium α grain boundaries enriched by κ-phase precipitates controlled the tracer element diffusion in a consistent manner with a specific activation energy.