The morphology and crystallography of E-(Al18Cr2Mg3) nano dispersoids in 7475 Al alloy have been studied by using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and electron tomography (ET). Seven distinct morphologies have been three-dimensionally distinguished at the nanoscale: (i) triangular plates on {111}Al, (ii) hexagonal plates on {111}Al, (iii) rods parallel to <110>Al, (iv) small tetrahedra with {111}Al facets, (v) small octahedra, (vi) spheres and (vii) irregular shapes. Twinning can contribute to the diverse morphologies of E nano dispersoids. The orientation relationships (ORs) between E nano dispersoids and Al matrix have been systematically investigated by selected area electron diffraction (SAED) patterns, HRTEM and matrix calculation. The results from the matrix calculation indicate the absence of clear ORs between E nano dispersoids and Al matrix in 7475 Al alloy.