Date of birth unknown, became monk in the Benedictine monastery of San Niccoló del Lido at Venice in 1153. When, in a military expedition of the Venetians in 1172, all the other members of the family of the Justiniani perished in the Ægean Sea near the Island of Chios, the Republic of Venice mourned over this disaster to so noble a family as over a public calamity. In order that the entire family might not die out, the Venetian Government sent Baron Morosin and Toma Falier as delegates to Alexander III, with the request to dispense Nicholas from his monastic vows. The dispensation was granted, and Nicholas married Anna, the daughter of Doge Michieli, becoming through her the parent of five new lines of his family. Shortly after 1179 he returned to the monastery of San Niccoló del Lido, having previously founded a convent for women on the Island of Aniano, where his wife took the veil. Both he and his wife died in the odour of sanctity, and were venerated by the people, though neither was ever formally beatified.
GENNARI, Notizie spettanti al Bl. Niccolo Giustiniani, monaco di S. Niccolo del Lido (Padua, 1794; Venice, 1845); GIUSTINIANO, Epistola ad Polycarpum, virum clarissimum in qua B. Nicholai Justiniani Veneti monachatus a fabulis vanisque commentis asseritur (Trent, 1746); MURATORI, Rerum Italicarum scriptores, XII, 293 and XXII, 503 sq.