He had already been member of the City Council of Treviso and, in 1266, had received the seignory of Feltre and Belluno from the local bishop, which Gherardo was to hold until his death.
A guelph exponent, in 1278 he signed an alliance with Padua, Cremona, Brescia, Parma, Modena and Ferrara against the Ghibelline Verona.
Gherardo's first move was to attack the Castelli's castles of Asolo, Cornuda and Monleopardo, and to destroy their city residence by treason.
When the cession was declared illegal by the commune, the latter called in the Republic of Venice by ceasing them Motta di Livenza (1291): this was the first mainland possession of the Serenissima.
He was also a patron of feasts and arts, housing in his courts numerous cultural figures, such as Dante Alighieri and Ferrarino da Ferrara.