His credits include entries in the Harry Potter, Command & Conquer, Dead Space, RuneScape, Evil Genius, EA Sports and Theme Park video game series, among numerous others.

In 2010 his score for the Harry Potter and the Half-Blood Prince video game received a BAFTA nomination[5] and won an International Film Music Critics Association (IFMCA) award.

[9] On July 15, 2020, Audible released an adaptation of the comic book series as a multi-part audio drama directed by Dirk Maggs with music by James Hannigan.

The voice cast included Gaiman as the Narrator, James McAvoy as Dream, Kat Dennings as Death, Taron Egerton as John Constantine, Michael Sheen as Lucifer, Riz Ahmed as the Corinthian, Andy Serkis as Matthew the Raven, Samantha Morton as Urania Blackwell, Bebe Neuwirth as The Siamese Cat, Arthur Darvill as William Shakespeare, and Justin Vivian Bond as Desire.

The production spent two months at #1 in The New York Times Best Seller list The follow-up, The Sandman: Act II, was released on 22 September 2021, and featured most of the original cast.

New additions to the cast included: Regé-Jean Page as Orpheus, Jeffrey Wright as Destiny, Brian Cox as Augustus, Emma Corrin as Thessaly, John Lithgow as Joshua Norton, David Tennant as Loki, Bill Nighy as Odin, Kristen Schaal as Delirium, Kevin Smith as Merv Pumpkinhead, and Niamh Walsh as Nuala.

At EA, Hannigan became involved in devising interactive music playback systems for video games during the early days of digital audio and streaming, and went on to form a strong working relationship with the company.

In the course of his career, Hannigan has worked with several well-known figures from the chip music and 8-bit gaming era, including Richard Joseph, Mark Knight, and Commodore 64 maestro, Martin Galway.

In 2013, James Hannigan founded popular yearly conference Game Music Connect with friend and industry commentator, John Broomhall.

Held each year at London’s Southbank Centre, the event partnered with PRS For Music, Playstation and British Academy of Film and Television Arts (BAFTA).

Running for three years between 2013 and 2015, events featured numerous panels with leading composers, and keynote speeches from industry executives from Electronic Arts, Sony Interactive Entertainment and others.

[24] The composer has talked at numerous conferences and events, including NY Comic Con alongside Neil Gaiman, Kat Dennings and James McAvoy, Musicworks and The BAFTA Interactive Festival.

[25] James Hannigan has spoken at the Royal College of Music, has joined panels at NY Comic Con [26] and academic conferences including Ludomusicology.

[27] In 2004, Hannigan wrote "Changing Our Tune", a cover article for the UK's Develop magazine, outlining some of the differences between scoring for games and conventional linear media forms such as film and television.

[33] In 2007, a collage of Hannigan's music entitled Welcome to Hogwarts[34] was added to Video Games Live debuting in London at the Royal Festival Hall on 22 October 2007, and featuring the Philharmonia orchestra.

[35] Hannigan's 'Soviet March' theme from Command and Conquer: Red Alert 3 was performed at 'A Night in Fantasia', by the Eminence Symphony Orchestra at the Sydney Entertainment Centre, Australia on 26 September 2009.