Daniels has said that he loves acting on stage because "it's tough and keeps you on your toes as an actor". He appeared in All's Well That Ends Well and As You Like It (1999–2000), and played Mercutio in a 1994 TV adaptation of Romeo and Juliet. Other theatre credits include Waiting for Godot (1994) and 900 Oneonta (1994), which earned him a nomination for Best Actor at the Evening Standard Awards. He also acted in Martin Yesterday (1998), for which he was nominated as Best Actor in the Manchester Evening News Theatre Awards, Naked (1998), Tales From Hollywood (2001), Three Sisters (2003), Iphigenia at Aulis (2004), The God of Hell (2005), and The Wild Duck (2005–2006). In 2006, Daniels appeared in Thérèse Raquin as Laurent, for which a reviewer labelled his performance "riveting". On 1 April 2018, Daniels appeared as Pontius Pilate in the NBC live musical, Jesus Christ Superstar Live in Concert!.