A. J. Pollock was born on December 5, 1987 to parents Al and Karen Pollock. His family lived an hour and forty minutes away from Foxboro, Massachusetts, and Pollock and his father would routinely make the trip to watch New England Patriots' home games.
Pollock attended Regional Hebron Andover Marlborough High School in his hometown of Hebron, Connecticut. At RHAM High, Pollock played basketball, soccer, and baseball. In his senior year, Pollock was a member of the National Honor Society. That year, he was named Gatorade Player of the Year in Connecticut, receiving the most votes for a Connecticut player since 1974, and was also named the state's Player of the Year by the coaches association. Pollock finished his high school baseball career with a .411 batting average, 55 RBI, 26 walks, 27 stolen bases and eight strikeouts over 248 at-bats.
Pollock attended the University of Notre Dame, where he played college baseball for the Notre Dame Fighting Irish as an outfielder and third baseman. Pollock was named a Freshman All-American, leading the team with a .372 batting average. Pollock was rated by Baseball America before his sophomore season as the league's second-best 2009 MLB prospect and best pure hitter. During his sophomore season, Pollock hit .352 and led the team in hitting and stolen bases and was a First-Team All-Big East Conference as a center fielder. Pollock then played in the summer for the Falmouth Commodores of the Cape Cod Baseball League where he hit .377 and was named MVP of the league. In his junior season at Notre Dame, Pollock hit .365, had an on-base percentage of .443, and a slugging percentage of .610. Pollock also made no errors in 159 chances and stole 21 bases in 25 tries. Pollock became second player ever to lead the team in batting average for three consecutive years.
The Arizona Diamondbacks selected Pollock in the first round of the 2009 Major League Baseball Draft.
He was invited to spring training in 2010, but broke his right elbow while attempting to make a diving catch. Pollock missed the entire season due to the injury.
Pollock was called up to the majors for the first time on April 18, 2012 and made his debut that day. Batting as a pinch hitter for Justin Upton, Pollock collected his first career MLB hit, a single, on April 23 against the Phillies. He would play in 31 games that season for the Diamondbacks, batting .247 with two home runs and eight RBI.
In 2013 Pollock batted .269 with 8 home runs and 38 RBI over the course of 137 games.
Pollock missed the second half of the 2014 season with an injury. Up to that point in the season, he was batting .302. In 2015, he was named a National League All-Star. He ended the season batting .315 with 20 home runs and 76 RBI. Pollock was signed to a two-year extension worth $10.25 million on February 8, 2016. Pollock broke his right elbow again at the end of spring training, this time on a slide at home plate, and missed most of the 2016 season.
On May 15, 2017, Pollock was placed on the 10-day disabled list due to a right groin strain.
Pollock played for the United States national baseball team at the 2011 Pan American Games.
Pollock became engaged to his girlfriend, Kate, in March 2014. They met at Notre Dame, where Kate played for the lacrosse team. They were married after the 2014 season.