The 30-year-old actress and her 39-year-old co-star are officially together, People reports.
Amanda and Thomas are currently filming together for the upcoming movie, but originally met while they were working on the off-Broadway production The Way We Get By in 2015.
Amanda split from Justin Long, her boyfriend of two years, last fall, and Thomas split from his wife Kimberly Hope in October 2015 after being married for eight years.
Amanda Seyfried Is Officially Dating Her 'Last Word' Co-Star Thomas Sadoski
Source: Just Jared