Hannan's work as a playwright has been produced by the Royal Shakespeare Company, the Old Vic and the National Theatre of Scotland in its inaugural season (2006).
His 1990 play The Evil Doers was produced by the Bush Theatre in London and won numerous prizes including a Time Out Award. In 1996 he was nominated for Lloyds Bank Playwright of the Year for Shining Souls which premiered at the Traverse, and in 2001/2 he was the Judith E. Wilson Visiting Fellow in Drama at the University of Cambridge.
In 2008 his first novel Missy was published in the UK and the US, winning the 2009 McKitterick Prize awarded by the Society of Authors for a debut novel.
The Three Musketeers and the Princess of Spain won the 2011 CATS Award (Critics' Award for Theatre in Scotland) for Best New Play. That same year The God of Soho opened at Shakespeare's Globe.
He often creates big central roles for women. The Guardian hailed Elizabeth Gordon Quinn as a "monstrous and magnificent heroine".
The same critic described the central character of Shining Souls as a kind of Mother Courage cum Marilyn Monroe of the post-industrial wastelands and called it a "funny and serious postmodern masterpiece."
"Hannan has a sheer verve which few writers, living or dead, can touch."
“His characters address worlds beyond this one so naturally they exert a force unusual in modern drama.”