Doping of GaN through ion implantation permits improved control of the dopant profile and dose, while it also modifies the film's mechanical properties such as microhardness. We discuss the effect of Si+- and Mg+-ion implantation on the mechanical properties of GaN films grown by electron cyclotron resonance plasma-assisted molecular beam epitaxy on sapphire substrates. The changes of the mechanical properties are studied using the static indentation method and they are discussed in conjunction with results from near-edge x-ray absorption fine-structure spectroscopy. Transmission electron microscopy is used for the microstructural characterization of selected implanted specimens. The static indentation test method was applied utilizing Vickers and Knoop diamond indenters. The microhardness results are absolved from the influence of the substrate through the implementation of a well-established deconvolution method. The elastoplastic response of the films are compared and discussed on the basis of the proportional specimen resistance model and the form of the indentation size effect curves.