 At the end of the 2008 season, O'Brien was named Northamptonshire's player of the year and was rewarded for his consistent performances with a three-year contract with the club.A representative of Northamptonshire CCC said "Niall, who has just returned from international duty, was in sensational form last season with the bat, scoring over 850 championship runs and piling on the runs in one-day competitions in a new pinch-hitter role".In a tour match against Australia during the 2009 Ashes in July 2009, O'Brien made scores of 30 and 58 in a match Northamptonshire lost.