The son of Azzo VI d'Este and a noblewoman from the Aldobrandeschi family, he married in 1225.

He became the leader of the Guelph forces in the March of Ancona and had to face the invasion of Duke Rainald of Spoleto during the War of the Keys in 1228–1230.

Azzo took the chance to capture Ferrara in 1242, after defeating Ezzelino III da Romano, and established his family's lordship in the city, which lasted until late Renaissance times.

In 1259, he again defeated Ezzelino and his Ghibellines troops in the Battle of Cassano.

He married two times, and had one son, Rinaldo (born after 1221), who was captured by Frederick II and died as prisoner in Apulia (1251).