He distinguished himself in the campaigns of Manuel I Komnenos (r. 1143–1180) against the Serbians, Hungarians, and Pechenegs in the years between 1150 and 1153.
He fell, having been isolated from his own troops, fighting alone against a band of Seljuk Turk soldiers of the Sultanate of Rum.
[1] John is known to have been present at the ecclesiastical councils convened at Constantinople in May 1157, March 1166, and January and February 1170.
[1][2] John Kantakouzenos was married to Maria Komnene, the eldest daughter of Manuel I's brother, the sebastokrator Andronikos Komnenos.
[3] A branch of the Byzantine Kantakouzenos may have later arrived in Romanian lands and became known as the Cantacuzino family.