The purpose of this paper is to study PR-semi-invariant warped product submanifolds of a paracosymplectic manifold M . We prove that the distributions associated with the definition of PR-semi-invariant warped product submanifold M are always integrable. A necessary and sufficient condition for an isometrically immersed PR-semi-invariant submanifold of M to be a PR-semi-invariant warped product submanifold is obtained in terms of the shape operator.Mathematics Subject Classification (2010). 53B25, 53B30, 53C25, 53D15.