Nikolaus's parents were Protestants, and he himself followed them at first, but he subsequently became a Catholic and, along with Cardinal Pázmány, his most serious rival at court, became a pillar of Catholicism, both religiously and politically.

At court, he opposed the two great Protestant champions of the period, Gabriel Bethlen and George I Rákóczi.

Matthias II made him a baron (1613), count of Bereg (1617), and lord-lieutenant (Hungarian: főispán) of the county of Zólyom and magister curiae regiae (1618).

When he had to hand over Munkács in 1622 to Gabriel Bethlen because of the Peace of Nikolsburg, he was compensated by the Emperor with 2 new lordships, namely Fraknó (today: Forchtenstein, Austria) and Kismarton (today: Eisenstadt, Austria).

In 1625 he officiated in the coronation of the Emperor Ferdinand II, who made him Palatine of Hungary, the highest political function in the country.