Abstract Single- and polycrystalline samples of LaAl2 doped with Gd in the concentration range 0 ⩽ c ⩽ 0.7 at% have been investigated by magnetization and ac susceptibility measurements. The depression of Tc with Gd concentration is in agreement with previous experimental work. Concerning the temperature dependence of Hc2, peaks at intermediate temperatures (∼400 mK) and downward curvatures towards T=0 are observed. The clean limit results can be explained quantitatively in terms of anisotropic Eliashberg theory for the upper critical field, with anisotropy parameters 〈a2〉 = 0.01 for the electron-phonon-coupling and 〈b2〉 = 0.16 for the Fermi velocity. Excellent agreement between theory and experiment can also be achieved for the Gd-doped materials, if spin orientation effects of the Gd atoms are included in the theoretical treatment.