In 1990 he returned to Ukraine where at his age of 92 he was elected the first Patriarch of Kiev and all Ukraine of the UAOC following its controversial and short-lived union with the recently proclaimed Ukrainian Orthodox Church - Kiev Patriarchy. He was enthroned as Patriach Mstyslav on November 6, 1990.
As the status of the new church as well as the overall situation with the Orthodox faith in Ukraine became a subject of the wide controversy, following the 1991 attainment of the Ukrainian independence (and continued to this day, see History of Christianity in Ukraine), the newly elected ailing patriarch was unable to alleviate any of the problems. He soon died (June 11, 1993) while back in Canada at the age of 95 and was buried in the [[Ukrainian Orthodox Church in the USA]] center in Bound Brook, New Jersey.
He was succeeded in UAOC by Patriarch Dymytriy (Yarema) while the Church matters and unity remain largely in disarray. The issue of repatriating Mstyslav's relics to Ukraine are occasionally raised but no firm plans are set in motion to this day.
before=[[Ioan (Theodorovych) of Philadelphia]]|
title=Primate and Metropolitan of the Ukrainian Orthodox Church of the USA|
after=[[Constantine (Bahan) of Irinoupolis]]}}