Abstract:For an orbifold $X$ and $\alpha \in H^3(X,Z)$, we introduce the twisted cohomology $H^*_c(X, \alpha)$ and prove that the non-commutative Chern character of Connes-Karoubi establishes an isomorphism between the twisted K-groups $K_\alpha^*(X) \otimes C$ and the twisted cohomology $H^*_c(X, \alpha)$.