Ultrathin gold nanowires (AuNWs) show prospects as components of materials for transparent and flexible electronics that exploit the wires’ high aspect ratio and mechanical flexibility. High junction resistances that are caused by the insulating oleylamine ligand shells and the wires’ intrinsic susceptibility to decomposition by the Rayleigh instability impede their use in the as-synthesized state. Treatment by H2/Ar plasma has been shown to improve conductivity and stability. We study the effects of a plasma treatment on morphology, chemistry, and temperature stability of AuNW layers by electron microscopy, X-ray diffraction, and Raman spectroscopy. Plasma treatment effectively removes oleylamine and sinters the individual ultrathin wires to superstructures with enhanced conductivity and temperature stability. Bundles of single ultrathin AuNWs can be sintered to continuous superstructures with enhanced conductivity and stability by H2/Ar plasma treatment.