Three-dimensional (3D) gold microarchitectures such as micropillars, microwires, and microlattices are used in applications such as implantable biosensors, microelectronic circuits, and catalytic devices. Additive Manufacturing (AM) is being explored to create such structures as lithography is more suitable to fabricate 2D or planar architectures. In this work, we use Aerosol Jet (AJ) nanoprinting, a jetting-based AM technique, to demonstrate fabrication of gold micropillars via stacking of nanoparticles and sintering them at temperatures ranging from 300°C to 900°C. We first demonstrate that AJ printed 2D planar films and 3D micropillars exhibit a different grain size distribution, even if they are printed and sintered under identical conditions. This unusual observation indicates that specific AM technique and structures are important in determining their grain structure, which affects their mechanical behavior. The AJ printed 3D gold micropillars are fabricated with aspect ratios up to 10:1 and sintered from lower to higher temperatures, to yield porosities ranging from 15 % to 2 %, and average grain sizes from 25 nm to 1.7 µm, respectively. Micropillars sintered at lower temperatures exhibit a brittle behavior with higher yield strength despite having a higher porosity but with smaller grain sizes, and vice versa. These results indicate that the 3D geometry of AJ printed architectures dictates the grain size evolution, and hence the mechanical properties. Further, the grain size dominates over porosity in determining the micropillar deformation. These results provide important design guidelines for 3D printed microarchitected structures fabricated via jetting-based AM techniques.