He was the son of Juan Téllez-Girón, 2nd Count of Ureña and Leonor de la Vega Velasco, daughter of Pedro Fernández de Velasco, 2nd Count of Haro. He married Mencía de Guzmán, daughter of Juan Alfonso Pérez de Guzmán, 3rd Duke of Medina Sidonia.
He was proclaimed unanimously Capitán General of the rebel army. In 1520, Pedro Girón led the comuneros army to Medina de Rioseco, establishing his headquarters at Villabrágima, only a mile away from the royalist army. On December 2, Pedro Girón moved his army from Villabrágima to Villalpando, and took that city without resistance.
But this manoeuver opened the road to Tordesillas for the royalist army, which in fact moved on Tordesillas and took it on December 5, overwhelming the small garrison left in the city.
The loss of Tordesillas was a serious setback for the comuneros, who lost access to Queen Juana I and the claim to fight in her name. Many leaders had also been captured or had fled.
Pedro Girón was blamed for his troop movement and was forced to abandon his command. On Resurrection Day, 1524, Pedro Girón was pardoned by King Charles I of Spain.
When his father died in 1528, he became 3rd Duke of Ureña.
He died 3 years later.
Pedro Girón had contacted the Junta de Tordesillas to defend his claims on the Duchy of Medina Sidonia, and became thus one of the leaders of the comuneros, together with Juan de Padilla and Antonio de Acuña.
