In this paper, we consider the dual Toeplitz operators on the orthogonal complement of the Fock–Sobolev space and characterize their boundedness and compactness. It turns out that the dual Toeplitz operator S f is bounded if and only if f ∈ L ∞ , and S f = f ∞ . We also obtain that the dual Toeplitz operator with L ∞ symbol on orthogonal complement of the Fock–Sobolev space is compact if and only if the corresponding symbol is equal to zero almost everywhere.