Abstract The effect of antiferromagnetic interchain coupling in alternating spin (1, 1 2 ) chains is studied by means of spin wave (SW) theory and density matrix renormalization group (DMRG). Two limiting cases are investigated, the two-leg ladder and its two-dimensional (2D) generalization. For the 2D case, SW approximation predicts a smooth-dimensional crossover keeping the ground state ordered, whereas in the ladder case the DMRG results show a gapped ground state for any J ⊥>0. Furthermore, the behavior of the correlation functions closely resemble the uniform spin- 1 2 ladder. However, for small J ⊥, the gap behaves quadratically as Δ∼0.6 J ⊥ 2. Similarly to uniform spin chains, it is conjectured an analogous spin gap behavior for an arbitrary number of mixed spin chains.