The 33-year-old, currently preparing for the World Cup, was named??the county’s cricketer of the year for 2014 after scoring 971 LV= County??Championship runs.
He also excelled in limited-overs cricket, scoring an unbeaten??century to help beat Hampshire in the Royal London One Day Cup.
O’Brien’s new deal bucks a trend for the county, who have lost talented players like Josh Cobb, Nathan Buck and Shiv Thakor since the end of last season.
O’Brien said: “I am delighted to commit my future to Leicestershire. It is the start of a new dawn at Grace Road and I am very pleased??to be a part of it.
“We are developing a good squad with a nice blend of youth and experience and??I am really looking forward to working with Wasim Khan, Andrew McDonald, all of??the coaching staff and my team-mates as we aim to have a successful season.”
Chief executive Khan said: “We see Niall as a key figure at the club. He is a??winner, has vast international experience and is a leader both in the dressing??room and on the field.”