He was part of the England Under-19 cricket team side for 2000 Under-19 World Cup held in Sri Lanka. Murtagh took 16 wickets at an average of 16.31 with the best bowling of 4/29 in three Youth Tests and 12 wickets at an average of 19.33 with the best bowling of 4/26 in 7 List A Internationals for the England Under-19 XI.

He played for Surrey as a backup bowler. After injuries to many of the Surrey bowlers in 2005, he has found himself having to lead the attack on several occasions. Murtagh took figures of 6/24 against Middlesex in the 2005 Twenty20 Cup which at the time that was his best bowling figures in the short form games.

Murtagh played in just two of Surrey's County Championship matches in the 2006 season. As a result, he searched for opportunities with other clubs.

Across seven seasons at Surrey, Murtagh played 34 first-class matches scoring 874 runs at an average of 32.37 and taking 68 wickets at an average of 37.72. He also played 65 List-A matches in which he took 79 wickets at an average of 32.63.

He signed a two-year contract with Middlesex in December 2006. Since moving to Middlesex, Murtagh's bowling average has significantly dropped. In first-class matches for Middlesex his wickets cost nearly twelve runs fewer than for Surrey and similarly his bowling average in List “A” matches for Middlesex is nine runs less than it was for Surrey.

Consistent in all forms of cricket and with a liking for the big occasion, he took 104 wickets in all three formats in 2008.

Surprisingly, he was overlooked for the England development squad, but had his chance to shine in Middlesex's trip to Antigua for the Stanford 20/20 for 20. Together with Steven Finn he led Middlesex's attack in 2011 helping them win promotion with 80 wickets at 20.98.

A conversation with Sussex and Ireland batsman Ed Joyce in 2011 led Murtagh to seriously consider qualifying for Ireland as his grandfather was born in Dublin. He applied for Irish citizenship in October that year, which was granted in January 2012.

Ireland's first engagement after Murtagh qualified was the 2012 ICC World Twenty20 Qualifier held in the UAE in March. Murtagh was named as a reserve in case any of the 14 players in the squad were injured. He made his debut against Australia in an a