The structural and electronic properties of N-doped zigzag graphene nanoribbons (N-ZGNRs) adsorbed on Si(001) substrates are investigated with first-principles density functional calculations. Compared with the free-standing N-ZGNRs, the energy difference between the substitutional doping at the edge and the inner sites is significantly decreased on the Si substrate. The distribution of the extra charge induced by the N substitutional dopant keeps the Friedel oscillation feature, and is a main effect that influences the C–Si bonding strength. When N is doped in regions with high C–Si bond densities, the strain induced by the dopant also plays an important role in determining the C–Si bonding interactions. Similar to the undoped case, the strong N-ZGNR/Si interaction destroys the antiferromagnetic coupling of the edge states in N-ZGNR, leading to a non-magnetic ground state for the N-ZGNR/Si heterostructures.