We consider the open superstring ending on a D-brane in the presence of a c
onstant NS-NS B field, using the Green-Schwarz formalism. Quantizing in the
light-cone gauge, we find that the anti-commutation relations for the ferm
ionic variables of superspace remain unmodified. We also derive the unbroke
n supersymmetry algebra living on the D-brane. This establishes how the Moy
al product is extended in a superspace formulation of non-commutative field
theories. The superfield formulation of non-commutative supersymmetric fie
ld theories is briefly considered.