The efficacy of laser annealing for the thermal annealing of nanocrystalline gold nanowires is evaluated. Continuous laser illumination at 532 nm, focused to a 0.5 μm diameter spot, was rastered perpendicular to the axis of nanocrystalline gold nanowire at ∼2 kHz. This rastered beam was then scanned down the nanowire at velocities from 7 to 112 nm/s. The influence on the electrical resistance of the gold nanowire of laser power, polarization, translation speed, and nanowire width were evaluated. Nanocrystalline gold nanowires were prepared on glass surfaces using the lithographically patterned nanowire electrodeposition (LPNE) method. These nanowires had a rectangular cross section with a height of 20 (± 3) nm and widths ranging from 76 to 274 nm. The 4-contact electrical resistance of the nanowire is measured in situ during laser annealing and a real-time decrease in electrical resistance of between 30 and 65% is observed, depending upon the laser power and scan rate along the nanowire. These resistance decreases are associated with an increase in the mean grain diameter within these nanowires, measured using transmission electron microscopy, of up to 300%. The observed decrease in the electrical resistance induced by laser annealing conforms to classical predictions based upon the reduction in grain boundary scattering induced by grain growth.