On 3 June 1353, aged 14, she married in person at Valladolid, Spain, King Peter of Castile. Previously, she had been married by proxy at Abbaye de Preuilly on 9 July 1352. They married because Peter wanted an alliance with France. It is believed by historians that King Peter had married his lover, the Castilian noble Maria de Padilla before his marriage to Blanche, though he did deny this. There were many difficulties in getting the money promised as a dowry for Blanche.