[1] In her youth, she visited the Abbey of Santa María la Real de Las Huelgas, founded by her parents,[2] several times.

After meeting the two sisters, their grandmother Eleanor of Aquitaine (who had been a queen consort of France herself) judged that Blanche's personality was more fit to fulfil the role.

[8] With French forces defeated at Lincoln in May 1217 and then routed on their way back to their London stronghold, Louis desperately needed the reinforcements from France.

Helped by Theobald IV of Champagne and the papal legate to France, Romano Bonaventura, she organized an army.

Twice more did Blanche have to muster an army to protect Capetian interests against rebellious nobles and Henry III of England.

Her enemies called her "Dame Hersent" (the wolf in the Roman de Renart)[7] In 1229, she was responsible for the Treaty of Paris,[1] in which Raymond VII, Count of Toulouse, submitted to Louis.

To prevent Henry III of England from gaining more French lands through marriage, Blanche denied him the first two brides he sought.

[12] Blanche had to chase Philip to try to stop him from raiding the important county, leaving Henry III to proceed without serious resistance.

[12] Henry besieged Mirabeau and proceeded to Bordeaux, apparently "securing" the south while also losing massive amounts of money and being forced to take loans.

[12] Although the local lords could not see Henry off, he was either unable or unwilling to commit to a large offensive investment and decided to return to Brittany, where he spent the remainder of his money on feasts.

[11] Henry's failure to make any significant impact with his invasions ultimately discouraged Mauclerc's rebellion, and, by 1234, he was firm in his support of Louis.

In 1233, Raymond of Toulouse was starting to chafe under the terms of the treaty of Paris, thus Blanche sent one of her knights, Giles of Flagy, to convince him to cooperate.

Upon his return to Paris, Blanche decided that a Provençal marriage would suit her son and help keep Toulouse in check.

To maintain better control over the new queen, Blanche dismissed the family and servants who had come to her wedding before the couple reached Paris.

Louis insisted on the burning of the Talmud and other Jewish books, but Blanche promised Rabbi Yechiel of Paris, who spoke for the Jews, that he and his goods were under her protection.

[18] The chanson Amours ou trop tard me suis pris, a prayer to the Virgin Mary, is often attributed to Blanche.

Blanche's selection as bride for Louis and travel to France is noted in Elizabeth Chadwick's The Autumn Throne and E. L. Konigsburg's A Proud Taste for Scarlet and Miniver.

Blanche and Isabella of Angoulême are the main characters in Jean Plaidy's novel The Battle of the Queens,[26] and she is briefly mentioned in Marcel Proust's Swann's Way, in a disaparaging way by Doctor Cottard and Brichot.

[28] She is a supporting character in the novel The Crown Rose by Fiona Avery, based on the life of her daughter Saint Isabelle of France.

Blanche is also a central antagonist in the fictional middle grade novel, The Inquisitor's Tale, written by Adam Gidwitz.

[29] An image of Blanche of Castile has been used on the home kit of French Rugby union team Stade Français since the 2008 season.

[30] During the 1950s French restaurateur Noël Corbu claimed that Blanche of Castile had deposited a treasure in Rennes-le-Château that was later discovered by Bérenger Saunière during the late 19th century.