The two first sparked romance rumors with a coffee date in his hometown of Tulsa, Oklahoma, in December. They then made their red carpet debut as a couple earlier this year at the 2020 Golden Globes in January. Bilson and Hader walked the carpet together, celebrating their newfound love and his second consecutive nomination for Best Performance by an Actor in a Television Series – Musical or Comedy for Barry.
The two kept a very private personal life and not much was known about their relationship.
The two actors co-starred in The To Do List in 2013, which was written and directed by Hader's then-wife, Maggie Carey. Hader and Carey split in 2017, and share three daughters together: Hannah, 10, Harper, 7, and Hayley, 5.
Bilson, meanwhile, is mom to 5-year-old daughter Briar Rose, whom she shares with ex Hayden Christensen. Prior to dating Hader, she was romantically linked to former Bachelor Nick Viall, after appearing on an episode of his podcast, The Viall Files, in July of last year.
For more on Hader and Bilson, watch below. People was first to report the split.