In television, Bell starred as Abraham Woodhull in the AMC historical drama series Turn: Washington's Spies (2014–2017).

He also appeared in Close and True, an ITV legal drama shown in 2000, which starred Robson Green, James Bolam, Kerry Ann Christiansen and Susan Jameson.

Also in 2005, he starred opposite Evan Rachel Wood in the Green Day video "Wake Me Up When September Ends", directed by Samuel Bayer.

In 2009, producers announced that Bell would play the title role in the motion capture film The Adventures of Tintin, alongside Andy Serkis and Daniel Craig.

In 2019, he had a supporting role as Bernie Taupin in the biographical musical film based on the life of Elton John, Rocketman.

Bell dated American actress Evan Rachel Wood for a year in 2005 after they had met at the Sundance Film Festival.

Wood was aware of the false claims that they had first met while co-starring in the music video for Green Day's song "Wake Me Up When September Ends" and has stated they were "already dating and very much in love by that point.

[24] Bell argued in court that Wood's story defied credibility, and accused her of "withholding our son from me for other reasons of her own invention.

"[25] In May 2023, Wood accepted terms for their son staying in Los Angeles with Bell, while seeing him "one extended weekend per month" and holidays.

[26] In late 2015, Bell began dating his Fantastic Four co-star Kate Mara,[27] and in January 2017 the couple became engaged.