Abstract: The superembedding technique is used to derive a simple form of the Dirac equations and of the corresponding action for the fermions on the worldvolumes of the M5, M2 and D3 branes in a generic D=11 or type IIB supergravity background with bulk and worldvolume fluxes. The knowledge of the explicit dependence on fluxes in the fermionic action on the M5 and D3 brane can be useful for the analysis of moduli stabilization in search for phenomenologically relevant implications of string theory.