The effect of ion‐exchange on the fracture behavior and the threshold load is investigated for radial crack initiation resulting from cube‐corner indentation. Both tin and air sides of the sodium aluminosilicate float glass are considered. The threshold load and mechanical properties are experimentally measured by nanoindentation. A qualitative explanation of crack initiation is developed by analyzing the stresses at the indentation site. The ion‐exchanged glasses show a lower threshold load for radial crack initiation with a cube‐corner indenter than the raw glass, and this is due to a higher crack driving stress for ion‐exchanged glasses. However, the compressive stress on the surface of the ion‐exchanged glasses can inhibit the expanding of the radial cracks. The air side always shows higher values for the threshold load than the tin side before and after ion‐exchange, which is in accordance with the calculated crack driving stress results.