[3] Garber originated roles in the Broadway productions of Sweeney Todd: The Demon Barber of Fleet Street in 1979 (as Anthony Hope), Noises Off in 1983 (as Garry LeJuene), Lend Me a Tenor in 1989 (as Max), Arcadia in 1995 (as Bernard Nightingale), and Art in 1998 (as Serge).

Other notable films include Sleepless in Seattle (1993), The First Wives Club (1996), Annie (1999), Legally Blonde (2001), Sicario (2015), Dark Waters (2019), and Happiest Season (2020).

He received further Emmy nominations for his portrayal of Sidney Luft in Life with Judy Garland: Me and My Shadows (2001) and for his guest roles in the sitcoms Frasier in 2001 and Will & Grace in 2005.

He has since joined the Arrowverse appearing as Martin Stein / Firestorm in the superhero series The Flash (2015–2017) and Legends of Tomorrow (2016–2017, 2021).

The group enjoyed moderate success, breaking into the Canadian Top 40 with a version of Bobby Gimby's song "Canada" (1967).

[13] In 1998, he co-starred on Broadway in the Tony Award-winning play Art with Alan Alda and Alfred Molina.

[14] In mid-2007, he played Garry Essendine in a production of Noël Coward's Present Laughter at Boston's Huntington Theatre.

[16] In January 2018, Garber replaced David Hyde Pierce as Horace Vandergelder in the Tony-winning Broadway revival of Hello, Dolly!

[19] His earlier film work includes Godspell (1973) as Jesus Christ (the part he played originally in the 1972 Canadian stage production) and Sleepless in Seattle (1993).

In James Cameron's Titanic (1997), he essayed a Mid-Ulster accent to play the shipbuilder Thomas Andrews.

In 2009, Garber voiced DC Comics supervillain Sinestro in the direct-to-video animated film Green Lantern: First Flight.

[31] Aside from the two crossovers, Garber made an independent return to The Flash in the season three episode "Duet" as the unnamed husband of gangster Digsy Foss (Jesse L. Martin) in a dreamworld.

He once again reprised his role as Martin Stein for a final time in a vocal cameo in the season nine episode "A New World, Part One".

[37] Garber is good friends with his Alias co-star Jennifer Garner and officiated her 2005 wedding to Ben Affleck.

[38] Source: Playbill[52] In addition to industry awards, Garber was appointed to the Order of Canada in 2022, with the rank of Officer.