By means of high resolution x‐ray diffraction and photoluminescence measurements we demonstrate that, as a result of hydrogen irradiation of GaAs1−xNx/GaAs, the original tensile strain of the as‐grown material is reversed into a compressive one and that, at the same time, N atoms are electronically passivated. We show that the amount of compressive strain is determined exclusively by N concentration. This compressive strain is caused by the formation of peculiar N‐H complexes and disappears after moderate annealing, while N electronic passivation still holds. These experimental results demonstrate that the lattice properties of fully‐hydrogenated GaAs1−xNx/GaAs are ruled by a H complex which is different and less stable than that responsible for electronic passivation of N in GaAs1−xNx/GaAs.