A polarized and depolarized dynamic light scattering analysis on gold nano-colloids prepared by laser ablation in water has been conducted. This technique allows a simultaneous measurement of the translational and rotational diffusivities and has been applied to characterize ‘as-prepared’ and aggregated colloids obtained either by “spontaneous” or with “controlled” procedure. A simple model was applied to obtain information on the size, shape and anisotropy properties of the nanoparticles directly in the liquid state. The ‘as-prepared’ Au nanoparticles (AuNPs) are spherical, while a prolate ellipsoidal shape can be attributed to the aggregated nanoparticles. Depolarized dynamic light scattering results a powerful technique to determine the size and shape of AuNPs directly in solution.