This article explores a novel operation of a monomial ideal, termed duplication, which produces a monomial ideal \(I^\diamond \) from another I. This operation is inspired by and generalizes how vertex duplication affects the edge ideal of a graph. The main result describes a multigraded minimal free resolution of \(I^\diamond \) as long as we know a resolution for I. Consequently, we obtain formulas for the projective dimension and depth of \(I^\diamond \) in terms of the corresponding invariants of I.
