After her father had been assassinated in 1584, her aunt Catherine took her to Arnstadt, while most of her sisters were raised by Louise de Coligny.

[2] In 1596, during a wedding feast in Dillenburg that lasted from 23 October - 3 November, she married Philip Louis II, Count of Hanau-Münzenberg, with whom she had ten children in just fifteen years.

When emperor Ferdinand II requested passage through Hanau for his coronation in Frankfurt in 1618, she refused him entry.

When king Gustavus Adolphus of Sweden liberated Hanau from Imperial occupation in 1631, it was Catharina Belgica who issued negotiations with the Swedish king and successfully secured the state for her son, and she guarded the alliance between Sweden and Hanau in cooperation with her daughter, the regent of Hesse-Cassel.

Her marriage with Philip Louis II of Hanau-Münzenberg produced 10 children, of which eight lived to adulthood: