Is cranberry juice good for constipation?

A little: Cranberry juice has sugar, which can help a little the way any juice can. Plus staying well hydrated is important. In regards to it's laxative power, not really. Cranberries themselves offer fiber the same way other berries do, and that is substantiative. However, juices have little fiber and aid little as a laxative.

Constipation: Yes. Cranberry juice is a form of added fluids to consume. However, its effect on the bowels is not as good as the fruit juices that also provide more fiber like prunes, pears, etc.