Andronicus' early years were spen in alternate pleasure and military service. In 1141 he was taken captive by the Seljuk Turks and remained in their hands for a year. On being ransomed he went to Constantinople, where was held the court of his cousin, the emperor Manuel, with whom he was a great favourite. Here the charms of his niece, the princess Eudoxia?, attracted him. She became his mistress, while her sister Theodora stood in a similar relation to the emperor Manuel.
In 1152, accompanied by Eudoxia, he set out for an important command in Cilicia?. Failing in his principal enterprise, an attack upon Mopsuestia, he returned, but was again appointed to the command of a province. This second post he seems also to have left after a short interval, for he appeared again in Constantinople, and narrowly escaped death at the hands of the brothers of Eudoxia.
About this time (1153) a conspiracy against the emperor, in which Andronicus participated, was discovered and he was thrown into prison. There he remained for about twelve years, during which time he made repeated but unsuccessful attempts to escape. At last, in 1165, he was successful; and, after passing through many dangers, reached the court of Yaroslav?, grand prince of Russia, at Kiev?. While under the protection of the grand prince, Andronicus brought about an alliance between him and the emperor Manuel, and so restored himself to the emperor's favour. With a Russian army he joined Manuel in the invasion of Hungary and assisted at the siege of Semlin?.
After a successful campaign Manuel and Andronicus returned together to Constantinople (1168); but a year after, Andronicus refused to take the oath of allegiance to the prince of Hungary, whom Manuel desired to become his successor. He was removed from court, but received the province of Cilicia.
Being still under the displeasure of the emperor, Andronicus fled to the court of Raymund, prince of Antioch. While residing here he captivated and seduced the beautiful daughter of the prince, Philippa, sister of the empress Maria. The anger of the emperor was again roused by this dishonour, and Andronicus was compelled to fly.
He took refuge with Amalric I of Jerusalem, whose favour he gained, and who invested him with the town of Berytus, now Beirut?. In Jerusalem he saw Theodora, the beautiful widow of the late king Baldwin? and niece of the emperor Manuel. Although Andronicus was at that time fifty-six years old, age had not diminished his charms, and Theodora became the next victim of his artful seduction. To avoid the vengeance of the emperor, she fled with him to the court of the sultan of Damascus; but not deeming themselves safe there, they continued their perilous journey through Persia and Turkestan?, round the Caspian Sea and across [Mount Caucasus]?, until at length they settled among the Turks on the borders of Trebizond?. Into that province Andronicus, with a body of adventurers, made frequent and successful incursions.
While Andronicus was on one of his incursions, his castle was surprised by the governor of Trebizond, and Theodora with her two children were captured and sent to Constantinople. To obtain their release Andronicus made abject submission to the emperor; and, appearing in chains before him, implored pardon. This he obtained, and was allowed to retire with Theodora into banishment in the little town of Oenoe, on the shores of the Black Sea.
In 1180 the emperor Manuel died, and was succeeded by his son Alexius II, who was under the guardianship of the empress Maria. Her conduct excited popular indignation; and the consequent disorders, amounting almost to civil war, gave an opportunity to the ambition of Andronicus. He left his retirement, secured the support of the army and marched upon Constantinople, where his advent was stained by a cruel massacre of the Latin inhabitants. Alexius was compelled to acknowledge him as colleague in the empire, but was soon put to death.
Andronicus, now (1183) sole emperor, married Agnes, widow of Alexius II, a child eleven years of age. His short reign was characterized by strong and wise measures. He resolved to suppress many abuses, but, above all things, to check feudalism and limit the power of the nobles. The people, who felt the severity of his laws, at the same time acknowledged their justice, and found themselves protected from the rapacity of their superiors. The aristocrats, however, were infuriated against him, and summoned to their aid [William of Sicily]?. This prince landed in Epirus? with a strong force, and marched as far as Thessalonica, which he took and destroyed; but he was shortly afterwards defeated, and compelled to return to Sicily.
Andronicus seems then to have resolved to exterminate the aristocracy, and his plans were nearly crowned with success. But in 1185, during his absence from the capital, his lieutenant ordered the arrest and execution of [Isaac Angelus]?, a descendant of the first Alexius. Isaac escaped and took refuge in the church of St Sophia. He appealed to the populace, and a tumult arose which spread rapidly over the whole city. When Andronicus arrived he found that his power was overthrown, and that Isaac had been proclaimed emperor. Isaac delivered him over to his enemies, and for three days he was exposed to their fury and resentment. At last they hung him up by the feet between two pillars. His dying agonies were shortened by an Italian soldier, who mercifully plunged a sword into his body. He died on the 12th of September 1185.