Ferdinand II, Holy Roman Emperor's proposal of marriage between Władysław and Archduchess Cecilia Renata of Austria (sister of future Ferdinand III, Holy Roman Emperor) arrived in Warsaw somewhere during spring 1636. In June that year, Władysław sent Jerzy Ossoliński to the Imperial Court, to work on improving the Imperial-Commonwealth relations. The king's trusted confessor, father Walerian Magni (of Franciscan religious order), and voivode Kasper Doenhoff arrived in Regensburg () on 26 October 1636 with consent and performed negotiations. The Archduchess' dowry was agreed for 100,000 złoty's, the Emperor also promised to pay the dowries of both of Siegmund III's wives: Anna and Konstance. Additionally the son of Władysław and Cecilia Renata was to obtain the duchy of Opole and Racibórz in Silesia (Duchy of Opole and Racibórz). However, before everything was confirmed and signed Ferdinand II died and Ferdinand III backed from giving the Silesian duchy to the son of Władysław. Instead a dowry was awarded to be secured by the Bohemian estates of Třeboň (Trebon). On 16 March 1637 a "family alliance" was signed between the Habsburgs and the Polish branch of the House of Vasa. Władysław promised not to sign any pacts against the Habsburgs, and to transfer his rights to the Swedish throne in case of his line's extinction; in return, Habsburg promised to support his efforts to regain the Swedish crown, and to transfer to him some territory in case of gains in a war against the Ottomans. The marriage took place in 1637, on 12 September.