We propose an N = 2 twisted superspace formalism with a central charge in four dimensions by introducing a Dirac–Kähler twist. Using this formalism, we construct an off-shell twisted hypermultiplet action and find an explicit form of fermionic scalar, vector and tensor transformations. We construct an off-shell Donaldson–Witten theory coupled to the twisted hypermultiplet. We show that this action possesses N = 4 twisted supersymmetry at the on-shell level. It turns out that the four-dimensional Dirac–Kähler twist is equivalent to Marcus' twist.