The deal comes a day after the 27-year-old filed for salary arbitration. Harrison was eligible for free agency after the 2014 season, but his new contract will keep him with the Rangers through at least 2017 and contains a team option for '18 that becomes a vesting option if Harrison reaches certain plateaus for innings pitched.
Harrison passed a physical on Wednesday night, and the Rangers announced the deal at a news conference Thursday.
Texas now has four starting pitchers under the age of 30 who are under contract or team control for at least the next four seasons. Alexei Ogando will be eligible for arbitration for the first time next year and can't become a free agent until 2017. Derek Holland is signed through '16, with two additional team option years, and Yu Darvish is signed through '17.
Harrison went 18-11 with a 3.29 ERA in 32 starts for Texas last season, throwing 213 1/3 innings. He made his first American League All-Star team and was the Rangers' Pitcher of the Year.
Originally a third-round pick by the Braves in the 2003 First-Year Player Draft, Harrison was acquired by Texas at the 2007 Trade Deadline as part of a deal for Mark Teixeira. In five seasons with the Rangers, the lefty has started 94 of his 126 games, going 48-30 with a 4.08 ERA and averages of 5.5 strikeouts and three walks per nine innings.
Andrew Simon is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.