We show that the degree of piecewise q-coconvex approximation E (q) n ( f, Y s ) of a q-convex function by algebraic polynomials of degree < n asymptotically depends only on α, Y s and q,assuming this inequality holds for an N * dependent on f and that the degree of unconstrained approximation has the same decrease rate: n α E n ( f ) ≤ 1, n ≥ N with N ≤ s + q + 1. In particular, cases α > 1, N = s + 2, q = 1, and α > 2, N = s + 3, q = 2 complement earlier results on comonotone and coconvex approximation by polynomials respectively.