She was the daughter of Michele Sbarra Morosini, Patrician of Venice. In 1263 she married Stephen the Posthumous, Prince of Hungary in Venice where he was living in exile. His paternity was disputed by his brothers born from their father's earlier marriage and he was not recognized as heir presumptive to the Hungarian throne. Tomasina gave birth to a son, Andrew III, King of Hungary (ruled 1290-1301), who was named after his grandfather, Andrew II. She supported her son's claim to the Hungarian throne. After the death of King Ladislaus IV, Prince Andrew succeeded to gain the kingdom and he was crowned King of Hungary in the name of Andrew III in 1290. He summoned his mother to Hungary and appointed her Princess of Slavonia. Allegedly she was poisoned in 1300, shortly before her son's death on 14 January 1301 which was also rumoured to have been caused by poisoning. He was the last king of the House of Arpad.
- Cawley, Charles, Medieval Lands Project/Venice/Tomasina Morosini, Medieval Lands database, Foundation for Medieval Genealogy
- Cawley, Charles, Medieval Lands Project/Hungary Kings Genealogy, Medieval Lands database, Foundation for Medieval Genealogy