When in August 1270, during the eighth crusade, died his father in Tunisia, victim of the plague, Felipe III was upon him there, so, after having achieved some advantages against Muslims, with the aid of the King of Sicily Carlos of Anjou, signed a ten-year truce with the emir Muhammad I and returned to France to take charge of the succession. This peace treaty managed to that peaceful and lucrative commercial relations restoration completely. The Hafsid emir returned to allow the return to Tunisia of the European consuls, responsible for protecting the interests of their Nations.
His first wife, Isabella of Aragon, daughter of Jaime Idied in the way back to Europe. Finally he/she came to France in 1271 and on August 15 it was consecrated in Rheims. That same year he/she took possession of the County of Toulouse, Raymond VII, which returned to the Crown on the death of his uncle Alfonso de Poitiers coast-to-coast, in accordance with the Treaty of Paris in 1229, in which the marriage of the daughter of Raimundo, Juana, was concluded with Alfonso of Poitiers and was guaranteed the annexation of Toulouse to the French Crown. The following year he/she repressed a rebellion of Roger, count of Foix.
Felipe III was weak health, low intelligence and little equipped for policy, leaving the Government in the hands of its support of camera, Pedro de la Bresse, which showered favours and titles, but which did not nothing to save him from the plot that was formed against her in 1278.
It maintained a diplomatic conflict with Eduardo I of England in relation to the legacy of Alfonso of Poitiers, which finally remained in the hands of the French King with the exception of the Agenais which was for Eduardo I.
In 1274 he/she intervened in Navarra in support of Blanche of Artois, widow of Henry I. This pressed by Castilla sought the help of France who achieved after the marriage of her daughter Joan of Navarre with Felipe the beautiful one in France. Subsequently intervened in Castile in favor of Blanche of France, his sister, whose husband, Fernando de La Cerda, son of Alfonso X, had died. White he/she sought the support of France to secure the succession of their children against Sancho IV, but failed.
In 1283 Carlos of Anjou offered to Felipe III, on behalf of the Pope, the Crown of Aragon. This accepted and began preparations for the invasion of the Kingdom, which took place the following year. On 26 June he/she laid siege to Gerona, but it could not take the city since 7 September it had to raise the site ravaged by disease and the continuous defeats suffered by both army and Navy responsible for equip it.
The retreating Felipe III suffered a dramatic defeat at the Coll de Panissars, and shortly thereafter died. His first marriage was to his successor Felipe IV, and Carlos. From his second marriage, to María de Brabante, was Luis, Margaret who married Eduardo I of England, and white, wife of Rodolfo de Austria.