This work explored the effect of spin projection on the quality of calculated J-coupling values and spin crossover gaps in transition metal complexes. Furthermore, the dependence of such calculations on geometry has been studied. A widely used test set of J-couplings for nine transition metal complexes was studied with and without applying spin-projection corrections. Our results show that spin-projection does not often result in large (qualitative) structural changes in the minimum energy structure relative to optimized spin-contaminated unrestricted DFT geometries. However, such differences can yield meaningful changes in energy and the use of geometries optimized with the AP method in J-coupling computations using either the spin-projected or non-projected approaches generally results in better agreement with experiment than using unoptimized crystal structure geometries. In addition, the NP method performed better than AP method in most cases, rationalized by considering that the magnitude of DFT energy calculation error is much larger than that of typical J-coupling values.