Marino Michiel is first attested as a witness in Venice in 1191. In 1215, he was a judge in Venice. He was then appointed as the Venetian Podestà of Constantinople. Attested in the office in March 1221, he was likely in stalled in autumn 1220, with a tenure lasting until spring 1222. He is last attested in 1250, when he was the Venetian Bailo of Negroponte.