Education
He then played for the English side Rotherham Titans in the RFU Championship where he became a stand out performer scoring eleven tries in the 2011-2012 season as they finished seventh in the table.
He then played for the English side Rotherham Titans in the RFU Championship where he became a stand out performer scoring eleven tries in the 2011-2012 season as they finished seventh in the table.
Monahan previous played for Leinster as an academy player and for Connacht in Ireland. Monahan signed a one-year deal to join Aviva Premiership side Gloucester Rugby for the 2012/13 season. His first highlight was scoring four tries in the Amlin Challenge Cup victory over London Irish.
On 2 April 2013, it was announced that Monahan had signed a two-year contract extension to keep him at Gloucester until the end of the 2014/15 season.
On 13 August 2015, it was announced that Irish Pro12 side Munster had signed Monahan on a short-term contract as cover during the 2015 Rugby World Cup. He made his debut for Munster on 5 September 2015, starting against Treviso.
Monahan left Munster in November 2015, upon the conclusion of his contract.