- Father is noted Maine landscape painter Neil Welliver.
- Made professional acting debut in the 1990 action/adventure movie Navy Seals.
- Made TV debut in the 1990 TNT movie The Lost Capone; played Al Capone a year later in the theatrical movie The Mobsters.
- Connection with writer/producers Steven Bochco and David Milch began with a guest role on a 1992 episode of L.A. Law. Also guested on three 1996 episodes of Murder One, was a semiregular on NYPD Blue (1995-98), and a regular on Brooklyn South (1996-97), Big Apple (2001) and Deadwood (2004-06).
- Laurence Fishburne was best man at his 1998 wedding.
- Appeared with Lost rival Mark Pellegrino in Twisted. The two also appeared in consecutive episodes of Prison Break (2008) and Supernatural (2009).
- A landscape painter himself, he has exhibited at galleries in Maine and Los Angeles.
- 2006, Screen Actors Guild Awards — Outstanding Performance by an Ensemble in a Drama Series: Nominee
- Eli Welliver — Brother
- Ashley Welliver — Sister
- Neil Welliver — Father
- Silas Welliver — Brother
- Norma Cripps — Mother
- Ethan A. Welliver — Brother
- John W. Welliver — Half Brother
- Quinnn M. Welliver — Son
- Elizabeth W. Alexander — Wife (deceased)
- Jose Stemkens — Wife
- Cora McBride Walling Welliver — Daughter
- Mimi Martin Welliver — Stepmother
- Eamonn Lorcan Charles Welliver — Son
- Joanna Heimbold — Ex-wife
- Attended Bennington College, Bennington, Vermont, United States; New York University, New York, New York, United States (BA in Drama)