Khashan’s study concerning a characterization of almost prime submodules is restricted to finitely generated multiplicative modules. In this paper, we give the description of almost prime submodules of a finitely generated free module over a principal ideal domain. The description will be divided into two cases, when the submodule’s rank is equal to the rank of its module and when the submodule’s rank is less than the rank of its module.

weakly prime submodule, almost prime submodule, torsion module, free module, principal ideal domain.