Delaney's works include the RTÉ television series Bachelors Walk as one of three bachelors living together in a flat on the quays in Dublin. The sitcom ran from 2001-2003 to positive reviews. He appeared as Grogan in On the Nose in 2001 along with Dan Aykroyd and Robbie Coltrane. He starred as the title character in the film Zonad by director John Carney. He gained increased prominence due to a high-profile part in the Tesco Mobile Ireland TV advertising campaign, in which he also spoke candidly of his battle with lactose intolerance. In 2009 and 2012, Delaney played Bill O'Brien in the cartoon ROY.
In October 2011, Delaney played an Anglo-Hiberno Lawyer in CBS's The Good Wife. In January 2012 he is due to appear in the upcoming US series Touch'. In September 2012, he appeared in new comedy seriesMoone Boyon Sky One.