  We express supersymmetric couplings among the vector and the tensor
multiplets in six dimensions (6D) in terms of N=1 superfields. The superfield
description is derived from the invariant action in the projective superspace.
The obtained expression is consistent with the known superfield actions of 6D
supersymmetric gauge theory and 5D Chern-Simons theory after the dimensional
reduction. Our result provides a crutial clue to the N=1 superfield description
of 6D supergravity.
