Nanomechanical measurements of platinum–carbon 3D nanoscale architectures grown via focused electron beam induced deposition (FEBID) were performed using a nanoindentation system in a scanning electron microscope (SEM) for simultaneous in situ imaging. Compression tests were used to estimate the modulus of the platinum–carbon deposits to be in the range of 8.6–10.5 GPa. Cantilever arm bend tests resulted in a modulus estimation of 15.6 GPa. Atomic layer deposition was used to conformally coat FEBID structures with a thin film of Al2O3, which strengthened the structures and increased the measured modulus. Cycled load-displacement testing at various load rates of nano-truss structures was also performed, demonstrating a viscoelastic response in the FEBID material. Finally, load-displacement tests of a variety of 3-dimensional nanoarchitectures with and without Al2O3 coatings were measured.