Seattle also came to terms with left-hander Jordan Shipers (16th round) out of South Harrison High School in Bethany, Mo., for $80,000 and right-hander Ernesto Zaragoza (25th round) out of Henry Kaiser High School in Riverside, Calif.
The Mariners have now signed 39 of 50 selections from the 2010 First-Year Player Draft, including first-round selection Taijwan Walker, a right-handed pitcher.
Littlewood was was selected 67th overall in the 2010 Draft. He was the earliest position player taken in MLB Draft history from the state of Utah.
He was named Utah's high school player of the year in 2010, hitting .538 with 10 doubles, eight home runs and 27 RBIs. He was a four-year starter at Pine View High School and was a two-time Deseret News Mr. Baseball award winner (2009 and '10).
Littlewood's father, Mike, has been the head baseball coach at Dixie State College since 1996. He played college baseball at BYU and was selected in the 27th round of the 1988 June Draft by the Milwaukee Brewers.
As of Monday night, the Mariners had signed eight of their top 10 choices and 16 of their top 20. Fourth-round pick James Paxton, a left-handed pitcher from Ladner, British Columbia, Canada, does not have any college eligibility remaining and has until a week prior to next year's Draft to agree to terms with the Mariners.
Seattle had hoped to sign third-round selection Ryne Stanek, a right-hander from Blue Valley North High School in Overland Park, Kan., and 11th-round pick Jon Keller, a right-hander from Xavier High School in Cedar Rapids, Iowa, before the 9 p.m. PT signing deadline.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.