- "I have to go back to work."
"It's part of the wedding: No Sicilian can refuse any request on his daughter's wedding day."
- ―Tom and Theresa Hagen[src]
- " This is my step brother Tom. That's his girl Theresa."
- ―Sonny Corleone introducing Carlo Rizzi to the family during Vito's 1941 birthday dinner.[src]
Theresa met Tom Hagen, the informal adopted son of Vito Corleone and his wife Carmela Corleone and married him in the late 1930s. They never divorced, despite Tom's affair with Judy Buchanan, although they were known to have had near at least one break-up and tumultuous arguments over Tom's affair and his business life, though they always reconciled. She was particularly close to her informal sister-in-law, Sandra Corleone, the wife of Sonny Corleone. She was a college graduate, intelligent, and articulate. She was an expert in art.
Theresa attended Vito Corleone's birthday dinner in 1941 where she set up the table, as well as the wedding of Connie Corleone and Carlo Rizzi in 1945. When Tom was kidnapped by Virgil Sollozzo, Theresa stayed at the Corleone compound until his return. She had four children with him, two sons Frank and Andrew, who were born before 1945, and two daughters, Christina who was born in 1954 and Gianna, who was born in 1959.
- "His mother, Theresa Hagen. Archbishop Gilday..."
"Honored to meet you."
- ―Michael Corleone introducing Archbishop Gilday and Theresa Hagen.[src]
In the 1960s, Theresa had became a noted art expert and helped found the Las Vegas Institute of Modern Art in the 1960s. When Judy Buchanan was murdered and Tom's extramarital affair was discovered, Theresa briefly moved away from him, taking their two daughters, who were not yet adults like their sons, with her to their home in Florida. The couple eventually reconciled and she accompanied Tom on his second visit to the Woltz mansion in Hollywood.
After Tom's death, Theresa remained close to her husband's adoptive family. She continued to appear at family venues, attending Michael Corleone's party, accompanied by her son Andrew, after Michael was awarded the Order of Saint Sebastian in 1979 where she met Archbishop Gilday.
Personality and traits
A kind-hearted and gentle woman, Theresa rarely lost her temper, even when she discovered her husband's affair. However she never fully recovered from this experience and behaved bitterly towards Tom for sometime before ultimately forgiving him. She valued spending time with family, including Tom's adopted family, even after Tom's death.