McClellan began writing when he was fifteen, starting at Wheel of Time role playing websites. He began working on short stories and novellas in his late teens, when he was encouraged toward writing by his parents.
McClellan went on to major in English with an emphasis on creative writing at Brigham Young University, where he met American author Brandon Sanderson, joining his writing classes. McClellan, wanting his writing to be more than just art, was determined to become a full-time writer. In 2006 he attended Orson Scott Card's Literary Bootcamp. In 2008 he received honorable mention in the Writers of the Future Contest.
McClellan published his first book, Promise of Blood, in 2013. The second book, The Crimson Campaign, has been released in May 2014. As of February 2015, his next novel, Autumn Republic concluded  the planned Powder Mage trilogy, with its UK publication.
The Powder Mage trilogy
Gods of Blood and Powder trilogy
- Sins of Empire (March 2017)
Nine novellas and short stories set in the world of The Powder Mage trilogy were released:
- Hope's End (2013)
- The Girl of Hrusch Avenue (2013)
- Forsworn (2014)
- The Face in the Window (2014)
- Servant of the Crown (2014)
- Murder at the Kinnen Hotel (2014)
- Return to Honor (2015)
- Green-Eyed Vipers (2015)
- Ghosts of the Tristan Basin (2016)
- Weimer, Paul (2013-04-03). "Interview:Brian McClellan Talks Epic Fantasy and "Promise of Blood"". SF Signal. Retrieved 2014-02-11.
- "Rob's Blog o' Stuff: Guest Post: Brian McClellan on Learning to Write from Brandon Sanderson". Robbedford.blogspot.be. 2013-04-08. Retrieved 2014-01-05.
- "» The Crimson Campaign". Brianmcclellan.com. 2013-05-06. Retrieved 2014-01-05.
- "» THE AUTUMN REPUBLIC – the exciting conclusion to the Powder Mage trilogy is out now!". Orbitbooks.net. 2015-02-12. Retrieved 2015-09-05.
- David Gemmell Legend Awards, 13 June 2014, retrieved 13 June 2014.