She was the niece of Michael Keroularios, Patriarch of Constantinople, whose sister had married John Makrembolites.
She married Constantine sometime before 1050. By him she had seven children; one died as a child and two, Konstantios and Zoe, were born after Constantine became Byzantine emperor in 1059. When Constantine died on May 22, 1067 she, as a crowned Augusta, was confirmed as regent for their sons Michael VII and Konstantios, along with Constantine's brother, the Caesar John Doukas. Michael VII was just old enough to rule on his own, but nevertheless was considered co-emperor with his younger brother, while Eudokia ran the administration of the empire.
She had also sworn on Constantine's deathbed not to marry again, and had even imprisoned and exiled Romanos Diogenes, who was suspected of aspiring to the throne. Perceiving that she was not able to avert the invasions which threatened the eastern frontier of the empire unaided, however, she revoked her oath and married Romanos, without the approval of John Doukas, the patriarch John Xiphilinos, or Michael VII. She approached the Patriarch John Xiphilinos and convinced him both to hand over the written oath she had signed to this effect, and to have him pronounce that he was in favour of a second marriage for the good of the state. The Senate then agreed to the marriage.
The wedding took place on January 1, 1068, and Romanus was immediately proclaimed co-emperor as Romanos IV. With his assistance Eudokia was able to dispel the impending danger. She had two sons with Romanos IV, Nikephoros and Leo. Another of Eudokia and Constantine's sons, Andronikos Doukas, was now made co-emperor by Romanos IV, although he had been excluded from power by his own father, mother, and brothers. However, Eudokia did not live very happily with her new husband, who was warlike and self-willed and increasingly excluded her from power.
When he was taken prisoner by the Seljuk Turks at the Battle of Manzikert (1071), Eudokia and Michael again assumed the government, until it was discovered that Romanos had survived and was returning to Constantinople. John Doukas and the Varangian Guard then compelled Eudokia to leave power to Michael and retire to a convent.
After Michael VII was deposed in 1078 by Nikephoros III, Eudokia was recalled by the new emperor, who offered to marry her. This plan did not come to pass, due to the opposition of the Caesar John Doukas, and Eudokia died as a nun sometime after the accession of Alexius I Comnenus in 1081.
The historian Nicephorus Gregoras, a century later, described Eudokia as a "second Hypatia".
Attributed to Eudokia is a dictionary of history and mythology, called Ἰωνιά (i.e. Collection or Bed of Violets). It is prefaced by an address to her husband Romanos Diogenes, and the work is described as "a collection of genealogies of gods, heroes, and heroines, of their metamorphoses, and of the fables and stories respecting them found in the ancients; containing also notices of various philosophers." However, the book is now thought to be a modern (16th-century) compilation, falsely attributed to Eudoxia, and compiled by the counterfeiter Constantine Paleocappa around 1540. The sources from which the work was compiled include Diogenes Laërtius and the Suda.
By her first marriage, to Constantine X Doukas, Eudokia had:Michael VII Doukas
Andronikos Doukas, co-emperor from 1068 to 1078
Konstantios Doukas, co-emperor from c. 1060 to 1078, died 1081
Anna Doukaina, a nun
Theodora Doukaina, who married Domenico Selvo, Doge of Venice
Zoe Doukaina, who married Adrianos Komnenos, a brother of Emperor Alexios I Komnenos.
By her second marriage, to Romanos IV Diogenes, Eudokia had:Nikephoros Diogenes
Michael Psellos was very close to the family, and Eudokia considered him an "uncle". According to Psellos she was very noble, beautiful, and intelligent.