In 1352, Wenceslaus married Joanna (1322 – 1406),[1] daughter of John III, Duke of Brabant and Limburg, and Marie d'Évreux.

In order to guarantee the indivisibility of Brabant, Wenceslaus signed the Joyous Entry, but had to fight against his brother-in-law Louis II of Flanders, who asserted his share of the duchy.

He failed to prevent the seizure of Brussels by the Flemings, but a certain Everard 't Serclaes succeeded by an audacious coup in driving them out of the city.

In 1371, he overestimated his military capacities and waged war with William II, Duke of Jülich, resulting in humiliating defeat at the Baesweiler, losing a part of his army, and several noblemen.

Wenceslaus I of Luxembourg wrote the lyric poetry interpolated in Jean Froissart's Méliador, which was identified as his by Auguste Longnon in the 1890s (Wenceslas was a patron of this chronicler).