ΔG = ΔH -TΔS
It all depends on the temperature and how big ΔH is relative to ΔS. In general, a more positive ΔS will make your ΔG tend toward negative, but it does not guarantee that ΔG will be negative, especially at low temperatures or if ΔH is large and positive. At high enough temperatures, however, reactions with positive ΔS should have a negative ΔG.