She married on 4 June 1570 in Heidelberg during the Diet of Speyer with Count Palatine John Casimir of Simmern (1543–1592).

August opposed the policies of John Casimir, who was a Calvinist and friendly to France.

With this marriage, August hoped to woo John Casimir over to the Lutheran side.

The Catholics in Germany regarded the marriage as a provocation against the Habsburg dynasty and an attempt to form a united Protestant front.

The Calvinist Johann Casimir tried to break the religious opposition of his Lutheran wife.