An experimental and analytical investigation of an axisymmetric turbulent wake with rotation was carried out. The axial and azimuthal (swirl) velocity fields were measured in the wake of a single 3-bladed model wind turbine with rotor diameter of 0.91m, up to 20 diameters downstream. The turbine was positioned in the free stream, near the entrance of the 6 m × 2.7 m cross section of the UNH Flow Physics Facility. Measurements were conducted at different rotor loading conditions with blade tip-speed ratios from 2.0 to 2.8. A pitot-static tube and constant temperature hot-wire anemometry with a multi-wire sensor were used to measure velocity fields. An equilibrium similarity theory for the turbulent axisymmetric wake with rotation was outlined, and first evidence for a new scaling function for the decay of the mean swirling velocity component, Wmax ∝ x−1 ∝ Uo3/2, was found.