The turbulence anisotropy in flow over noncohesive sediment beds at an entrainment threshold, as compared to that over immobile beds, is studied. The streamwise component of anisotropy tensor in near-bed flow for threshold beds yields more anisotropic stream as compared to that for immobile beds, whereas all other components of anisotropy tensor in near-bed flow for threshold beds yield less anisotropic stream. The anisotropic invariant maps illustrate the anisotropy in near-bed flow layer tending to be a two-component isotropy for both immobile and threshold beds. The data plots for immobile beds with an increase in vertical distance have an affinity to a one-component isotropy, whereas those for mobile beds show a tendency to become a three-dimensional isotropy near the midportion of the flow depth. Invariant function plots show a better two-dimensional isotropy in the inner layer of flow and a quasi-three-dimensional isotropy in the outer layer of flow over threshold beds than those over immobile beds. © 2015 American Society of Civil Engineers.