She was one of the protagonists, along with her brothers and her daughter Beatrice, of the events that led to the succession crisis of 1383–1385, which culminated in the defeat of her son-in-law King John I of Castile and his armies in the Battle of Aljubarrota.

According to some sources, she was born in Trás-os-Montes because King Ferdinand I on 3 January 1375 donated Vila Real to his wife "for being a native of the province of Tralosmontes".

[12] Leonor had three full-siblings: two brothers—João Afonso Telo (6th Count of Barcelos, mayor of Lisbon in 1372 and admiral of the Portuguese kingdom around 1375,[11] who died in the Battle of Aljubarrota)[13] and Gonçalo Teles de Meneses (Count of Neiva and Lord of Faria)[14][15][13]—and a sister—Maria Teles de Meneses,[16][17] who was married first to Álvaro Dias de Sousa and then to John of Portugal,[13] an illegitimate half-brother of Leonor's husband King Ferdinand I. Maria was murdered in 1379 by her second husband, who accused her of adultery; historians suspect that Leonor, fearing for the succession of her daughter Beatrice and her own position as regent, was involved in the crime.

[18][19] Maria was a lady-in-waiting of her future sister-in-law Beatrice of Portugal, and introduced Leonor to King Ferdinand I, who fell passionately in love with her, when she visited her sister in court.

Leonor arranged her marriage to Juan Alfonso Pimentel,[21] first Count of Benavente, who supported the cause of the Castilian king during the succession crisis and went into exile in Castile.

[24] In 1365, Leonor had wed João Lourenço da Cunha,[25] 2nd Lord of Pombeiro,[26][27] to whom she was still married when she met King Ferdinand I of Portugal.

Two children were born of her union with João Lourenço: a daughter who died in infancy, and a son, Álvaro da Cunha,[28] heir to the lordship of his father.

[30][b] King Ferdinand I subsequently attempted to obtain the annulment of Leonor's first marriage on the grounds of consanguinity, in order to preserve the legitimacy of their daughter, Beatrice of Portugal.

The Cortes determined that, since all pretenders to the throne, that is, the sons of Inês de Castro and the master of Aviz, were illegitimate, the dynastic line had been severed and the people, through their representatives, could choose a new king.

[34] From the beginning, John and Denis of Portugal, the sons of Inês de Castro and half-brothers of the king, showed their rejection of this marriage, as well as the "rise of Leonor and her relatives".

[29] King Ferdinand had given Leonor in the arras charter of January 1372 several cities,[36] all associated with the lordships of the queens of Portugal, among them Abrantes, Alenquer, Torres Vedras, Vila Viçosa, Almada, Sintra, Atouguia, Óbidos, Sacavém, Frielas and Unhos, which also included their houses, ports, fishmongers, royal rights, and other goods, and in April of the same year he also gave her Aveiro.

[37] In February 1373, during the brief siege that the Castilian troops imposed on the city in the second Fernandine War, Leonor gave birth in Coimbra to her first child with the king, a daughter called Beatrice.

[43][44] While the king and his counselors were in Elvas to discuss a new war with Castile, on 19 July 1382, Leonor gave birth to a son who lived only four days, dying under mysterious circumstances; some observers say it was due to the sultry weather in the Alentejo region during that summer, while others, including Fernão Lopes, said that Ferdinand I, suspecting the infidelity of his wife, had thought the child was the son of Andeiro and in a fit of anger suffocated the newborn prince in his cradle.

[45] On 27 September 1383 Leonor gave birth to a daughter who lived only a few days;[46][47] as in the previous case, it was also rumored that, due to King Ferdinand's long illness, he was not the infant's father.

[47] Leonor did not attend the funeral, according to the chronicler Fernão Lopes, "saying that she felt ill, and could not be there", because of her recent childbirth, or according to other commentators, "fearing the murmur of the people.

[50] In Lisbon, supporters of the master of Aviz who refused to recognize Beatrice as queen for fear of Portugal's loss of independence, organized a conspiracy to assassinate Juan Fernández Andeiro.

[66] Portuguese historian Joze Barbosa, in his work Catalogo das Rainhas de Portugal, said that she died on 27 April 1386 in Tordesillas and that she was buried in a convent in Valladolid, without specifying which one.

[50][67] However, there is evidence that Leonor was still alive in 1390 when her son-in-law, King John I of Castile, in the Cortes that were held that year in Guadalajara, included her in the expenses of his household.

In his last will executed in July 1385, King John I entrusted his son, the future Henry III of Castile, with the responsibility of always honoring his wife Beatrice and his mother-in-law Leonor Teles.