After her husband's death, she ruled both the kingdom and the county as regent for three years in the name of their son, Theobald II of Navarre.

[3] Her husband's death in 1253, however, brought her to spotlight: their son, Theobald II of Navarre, was 14, while the laws of the realm required the king to be 21 to take control of his inheritance.

Although her husband, also Count of Champagne, had resided in Navarre much of the time after his accession to the royal throne, the nobility of the kingdom were unwilling to accept his son as their king.

[3][4] Margaret prevented the outbreak of an open rebellion by travelling with Theobald to the capital, Pamplona,[3] and by allying with the neighbouring Kingdom of Aragon.

No longer regent, Queen Margaret retired to her large dower lands, consisting of seven castellanies (as much as a third of the comital revenues), where she spent the rest of her life.