Gallagher started his career as a presenter and sports reporter on BBC Radio Kent. He was a performer and puppeteer on Playhouse Disney and also provided characters and voices for Studio Disney.
From 2003 until 2005, Gallagher presented Diggin' It on GMTV. During 2006, he was a regular character on Mighty Truck of Stuff as 'Pablo', and was also the voice-over for Channel 4's Unanimous.
Gallagher has appeared as the title character in Mister Maker since 2007. He also appeared in 2 episode of Bear Behaving Badly as the Robot Rat Catcher and the Mummy. Since 2009, he has also played the role of 'Mr Liker Biker' in Grandpa In My Pocket.
Gallagher often performs in pantomimes. In 2006, he appeared as Wishee Washee in Aladdin at the Theatre Royal in Winchester. In 2007, he appeared as Silly Billy (Jack's brother) in Jack and the Beanstalk, again at the Theatre Royal in Winchester. In 2008, he appeared as Buttons in Cinderella at the Opera House, Buxton, Derbyshire. In 2009 he played alongside George Takei in the title role of Aladdin at the Central Theatre in Chatham, Kent, and in 2011 as Muddles in Snow White and the Seven Dwarfs in St Albans with Toyah Wilcox who played the Evil Queen. In 2013, he returned to Jack and the Beanstalk, playing Billy Trot in a production at the Marlowe Theatre, Canterbury alongside Samantha Womack.
- "Profile: Phil Gallagher (2)". Second Skin Agency. Retrieved 17 March 2010.
- "Profile: Phil Gallagher (1)". Second Skin Agency. Retrieved 17 March 2010.
- "Phil Gallagher's CV". Second Skin Agency. Retrieved 17 March 2010.
- Hannam, John (14 December 2006). "Aladdin". The Stage (The Stage Newspaper Limited). Retrieved 17 March 2010.
- "Jack and the Beanstalk – A sky high adventure". Easier Network. 22 November 2007. Retrieved 17 March 2010. "Children will recognise actor and presenter Phil Gallagher, the star of CBeebies Mister Maker, who returns to play Jack’s brother Silly Billy"
- "Winchester pantomime launched". News Extra Winchester (Newsquest). 25 September 2007. Retrieved 17 March 2010.
- Hannam, John (10 December 2007). "Jack and the Beanstalk". The Stage (The Stage Newspaper Limited). Retrieved 17 March 2010.
- Licence, Paul (27 December 2008). "Magic in the air at Buxton Opera House". Sheffield Star (Johnston Press). Retrieved 17 March 2010.
- "Past Winners and Nominees - Children's - Awards - 2009". BAFTA. Retrieved 17 March 2010.