An optical whole-field 3D particle tracking velocimetry tool for diagnostics in microgravity experiments is presented. To demonstrate the potential of the technique it is applied to a Marangoni convection experiment and to a flow within a fluid column, as typical microgravity experiments. In experiments under gravity conditions in an observation volume for the Marangoni experiment of 20×14×14 mm³, 200-500 velocity vectors per time instant could be determined, whereas in the fluid column experiment the observation volume was 40×40×15 mm³, and up to 850 velocity vectors per time instant could be determined.