From 1452 on Mocenigo followed a political career, being elected as a member of the
Venetian Senate, and then appointed ambassador to
Ibrahim II of Karaman to negotiate a commercial treaty and possibly an anti-
Ottoman alliance in 1453–1454 (although the identification of the Venetian ambassador with Mocenigo is not entirely certain), and head of the annual
trade convoy to
Alexandria in June 1454. In 1463, he was (governor) and captain of
Ravenna, then in 1466. From the latter position he was sent to negotiate an alliance with
Borso d'Este,
Lord of Ferrara, against the
Republic of Florence. He was re-elected as for the first half of 1467, and then immediately appointed of
Treviso. In November 1469 he was elected an , but held the office for a few weeks before being appointed (governor) of the
Patria del Friuli, serving until August 1471. In late 1471 Mocenigo was again , and then again in 1472. In 1474 he was a , before being sent, along with Andrea Vendramin and Antonio Venier, to negotiate the extension of the
Peace of Lodi with Florence and the
Duchy of Milan. Giovanni Mocenigo participated in the election of
Nicolò Tron as
Doge of Venice in November 1471, as well as the election of
Nicolò Marcello in July 1473, when he unsuccessfully promoted the candidacy of his brother,
Pietro. Pietro was more successful in December 1474, and was elected Doge, thus further enhancing Giovanni's position as well: from 1475 until his own election as Doge in 1478, he was consistently elected as a . Notably, he never held the post of
Procurator of Saint Mark before becoming Doge. In November 1477 he was member of a commission of senators sent to examine the defences of Friuli against a possible Ottoman attack. After the death of Doge
Andrea Vendramin on 6 May 1478, Mocenigo was elected as Doge on 18 May. His election was in large part to his popularity for his upright character rather than any political skills, and was won with crucial support of Marco Corner, the brother-in-law of Mocenigo's brother Nicolò. ==Dogate==