We deal with a weakly coupled system of ODEs of the type x j + n 2 j x j + h j (x 1 ,. .. , x d) = p j (t), j = 1,. .. , d, with h j locally Lipschitz continuous and bounded, p j continuous and 2π-periodic, n j ∈ N (so that the system is at resonance). By means of a Lyapunov function approach for discrete dynamical systems, we prove the existence of unbounded solutions, when either global or asymptotic conditions on the coupling terms h 1 ,. .. , h d are assumed.