Usually. A stable portal or, worse, portals might require some kind of guardian, and cover-ups to prevent its being noticed.
Still more if it's not just a portal, if there are regions where the worlds overlap.
Easier than in the sort of world where magic is everywhere and everywhere secret. Especially if the overlap means there are magical regions that have no contact with the mundane world, where things can be much more easily hidden. And preventing invasion might easily encourage the masquerade. Though it would make it easier to hold off trouble, too. . . .