As a loyal partisan of King John Zápolya, he served as de facto the last Bishop of Csanád between 1537 and 1552, before the Ottoman Empire conquered the southern parts of the Kingdom of Hungary, including the whole territory of the diocese.
János (IV) was born into a Transylvanian noble family in Csesztve, Kingdom of Hungary (present-day Cisteiu de Mureș, Romania) in 1482.
[2] Some of the members of his family (for instance, his grandfather János II and uncle Lénárd) financially supported that Humanist scholar circle, which centered around Gyulafehérvár (Alba Iulia).
[3][5] Joining the local Humanist circle, Barlabássy financially supported the construction of the Lazo chapel within the St. Michael's Cathedral of Gyulafehérvár, built by his relative János Lászai.
[6] Beside his rank of canon at the cathedral chapter of Transylvania, Barlabássy was elevated into the church offices of archdeacon of Szentkirály and Gombás (present-day Sâncrai and Gâmbaș, respectively) by 19 September 1518, when bought portions and a mill at Csombord (Ciumbrud).
The voivode instructed János and his brother Mihály in December 1512 to hand over the paternal property belonging to their step-mother Magdolna Erdélyi (their father's widow) and her children.
[4] Following the death of Giovanni Bonzagno, King John Zápolya and his spouse, Queen Isabella Jagiellon appointed János Barlabássy as Bishop of Csanád in 1537.
Pope Paul also instructed Cardinal Girolamo Aleandro to explain the reason for the confirmations of Barlabássy and other pro-John bishops to Ferdinand, who resented the decision of the Roman Curia.
As an atonement, Pope Paul III decided to spend procuratio (appointment fee) on maintaining the southern military frontier castle system along the border with the Ottoman Empire.
The Turks invaded and occupied the southern parts of the kingdom, including the whole territory of the Diocese of Csanád, which de facto ceased to exist.