Infrared absorption measurements of localized vibrational modes (LVM) due to Al in ZnSe performed under high‐resolution conditions reveal additional features as compared to previous data. The cluster of bands near 340 cm−1is resolved into at least six and possibly eight individual absorptions. A Green’s function calculation over various pertinent models best explains most of these LVM as probably arising from a (2 AlZn‐ZnSe) antisite complex (or at least an AlZnpair) with other complexes less likely. The linewidth of individual features can be explained in terms of nearest‐neighbor Se host lattice isotopes. Finally, features perturbed from the isolated AlZncase are considered as well as the remaining LVM of unknown origin.