The variety ddpM of de Morgan algebras with double demi-pseudocomplem-entation consists of those algebras (L;∧,∨,? ,* ,+ , 0, 1) of type (2, 2, 1, 1, 1, 0, 0) where (L; ∧,∨,? , 0, 1) is a de Morgan algebra, (L;∧,∨, *,+ , 0, 1) is a double demi-p-lattice and the operations x → x?, x → x* and x → x+ are linked by the identities x*? = x?*, x+? = x?+ and x*+ = x+*. In this paper, we characterize congruences on a ddpM-algebra, and give a description of the subdirectly irreducible algebras.