James Anthony Loney was born on May 7, 1984 in Houston, Texas, to Marion, known as Tony, and Annie Loney. His father was a computer programmer and software consultant and his mother worked as a teacher. Loney has a younger brother named Anthony.
Loney played baseball on a team sponsored by the Reviving Baseball in Inner Cities program and was coached at Elkins High School by Matt Carpenter's father Rick. In Loney's senior year, his high school team was ranked first in the nation by Baseball America and won the 5A state championship. Loney contributed a 12–1 record with a 1.52 ERA and 120 strikeouts as a pitcher that season, as well as a .500 batting average, eight home runs, 38 runs scored and 58 runs batted in. He was named to the Texas Sports Writers Association 5A all-state team at the end of the 2002 baseball season, as well as Powerade and Gatorade Player of the Year.
Much of the professional interest in Loney centered on his pitching ability, but he was drafted by the Los Angeles Dodgers in the first round, #19 overall, of the 2002 Major League Baseball draft as a position player. He had signed with Baylor University to play college baseball, but opted to sign a pro contract.
Loney began his professional career in 2002 with the Great Falls Dodgers, where he hit .371 and was named the top prospect in the Pioneer League by Baseball America. Loney also appeared in 17 games that year for Single-A Vero Beach, batting .299. He returned to Vero Beach for 2003, and in 125 games he hit .276 with 7 homers and 46 RBIs. He was listed #34 on the 2003 edition of Baseball America's Top 100 Prospects list.
In 2004, Loney was highly ranked for his defensive ability in the Arizona Fall League and made the All-Prospect Team voted on by league managers and coaches. However, he had an injury plagued season at Double-A Jacksonville and fell to #42 on Baseball America's prospect list. In 2005, Loney led the Southern League Champion Jacksonville Suns in hits and total bases. That season, he was ranked #62 on Baseball America's list of top prospects.
In 2006, Loney led all of baseball, major and minor leagues, with a .380 average while playing for the Triple-A Las Vegas 51s. He was named the Dodgers Minor League Player of the Year, and was chosen as first-team Triple-A All-Star First Baseman by Baseball America.
In the spring of 2016 he played briefly for the triple A, El Paso Chihuahuas for several months until the San Diego Padres traded him to the New York Mets . Loney immediately began playing MLB ball, first base for the Mets.
Loney made his major league debut with the Dodgers on April 4, 2006, against the Atlanta Braves. He received his opportunity when starting Dodgers first baseman Nomar Garciaparra was placed on the disabled list, freeing up a roster spot for Loney. Loney collected a single in his first major league at bat, against John Smoltz.
On September 28, in a game against the Colorado Rockies, Loney went 4 for 5 with 9 runs batted in, which tied a 56-year Dodgers franchise record for RBI in a single game, held by Gil Hodges. Loney accomplished this feat in only his 46th game with the team while still under 100 total at bats in his major league career. Because of his success in 2006 with both Los Angeles and Triple-A Las Vegas, he was named to the Dodgers' playoff roster. Filling in for an injured Garciaparra in game three against the New York Mets in the National League Division Series, Loney went 3-for-4 with three RBIs.
Despite Loney's stellar 2006 season, the Dodgers chose to re-sign Garciaparra for 2007–08, meaning Loney had to start the season back at Triple-A Las Vegas. On June 10, 2007, Loney was recalled to the Dodgers. His hot hitting forced the Dodgers to insert him into the starting lineup and move Garciaparra from first base to third base.
Loney hit nine home runs in September 2007, setting a Dodgers record for home runs by a rookie in a calendar month that he shares with Joc Pederson (May 2015). Loney was named the National League Rookie of the Month for September and finished sixth in the voting for the 2007 NL Sporting News Rookie of the Year Award.
Loney was a unanimous selection to the 2007 Topps Major League Rookie All-Star Team. The selection was the result of the 49th annual Topps balloting of major league managers.
Loney began the season as the starting first baseman and had a 15-game hitting streak. He finished the season batting .289 with 13 HR and 90 RBIs. Loney led the team in runs batted in consistently for the entire year. On October 1, 2008, in Game 1 of the National League Division Series, Loney hit a grand slam off of Chicago Cubs pitcher Ryan Dempster as the Dodgers went on to win the game 7–2.
Loney turned in numbers in 2009 similar to his 2008 numbers, hitting .281 with 13 home runs in 158 games as the team's starting first baseman. On January 19, 2010, Loney agreed to a new 1-year contract that substantially increased his salary from $465,000 to $3,100,000. In 160 games in 2010, he hit 10 home runs and 88 RBI, while batting .268, his poorest stats since he joined the team.
On September 16, 2011 Loney hit a three-run pinch hit home run in his only plate appearance and the following day hit another three-run homer. He set a career high with five hits on September 18, helping the Dodgers win three straight games against the Pittsburgh Pirates. Loney finished the season by hitting .288 with 12 home runs, though his RBI total of 65 was the lowest since his rookie season.
In 2012, Loney continued his downward career slide, hitting .254 with only 4 homers and 33 RBI in 114 games with the Dodgers. Around mid-season he started platooning at first base with Juan Rivera.
On August 25, 2012, he was traded to the Boston Red Sox (along with Iván DeJesús, Jr., Allen Webster, Jerry Sands and Rubby De La Rosa) for Adrian Gonzalez, Josh Beckett, Carl Crawford and Nick Punto and $11 million in cash. He played in 30 games with the Red Sox and hit .240
On December 6, 2012, Loney finalized a one-year $2 million deal with the Tampa Bay Rays. On July 23, 2013, Loney collected his 1,000th career hit in a game versus his former team, the Boston Red Sox. The contract wound up being a good deal for Loney and the Rays, as he hit .299 with 13 home runs and 75 RBIs, his best numbers since his rookie season in 2007. On December 13, 2013, Loney and the Rays agreed to a three-year contract worth $21 million. His numbers dipped a bit in 2014, as he hit .290 with 9 home runs and 69 RBIs, but he had 600 at-bats in a season for the first time in his career.
Loney was limited to 104 games in 2015 because of injuries. He only slashed .280/.322/.357 for his lowest OPS since 2012, in addition to a drop in defensive value to a −5.4 UZR/150 at first base. On March 30, 2016, Loney was informed that he would not be listed on the Rays Opening Day roster. On April 3, the Rays released Loney, eating the entirety of the $8 million owed to him for the 2016 season.
On April 7, 2016, Loney signed a minor league deal with the San Diego Padres. He played for the Pacific Coast triple A Team, the El Paso Chihuahuas.
On May 28, 2016, Loney was traded to the New York Mets for cash considerations.
On January 24, 2017, Loney signed a minor league contract with the Texas Rangers that included an invitation to spring training. The Rangers released Loney on March 27, 2017.
On April 12, 2017, Loney signed a minor league contract with the Detroit Tigers. He was released by Detroit on May 7, 2017, after batting .229 in 16 games with the Toledo Mud Hens, Detroit's AAA affiliate.
The Braves signed Loney to a minor league deal on May 18, 2017. Loney was released on May 22, 2017 following the Braves acquisition of first-baseman Matt Adams from the St. Louis Cardinals
Loney signed with the LG Twins of the KBO League for a $350,000 contract on July 18, 2017. After playing in 23 games, the Twins demoted Loney to the minor league. He opted to leave South Korea and return to the United States rather than report.
He married his wife, Nadia, an Iranian American, in 2013 and they have two sons. They live in San Diego, California in the off season.