On December 8, 2011, the Cubs traded LeMahieu and Tyler Colvin to the Colorado Rockies for Casey Weathers and Ian Stewart.
He began the 2012 season with the Colorado Springs Sky Sox of the PCL.

On May 23, 2012, LeMahieu was called up to the major leagues to replace injured Jonathan Herrera as a utility infielder.
He returned to Colorado Springs when Herrera was activated, and was recalled to the Rockies on July 17 when Chris Nelson was hospitalized.
On August 14, he recorded a career-best four hits in a 9–6 Rockies win over the Milwaukee Brewers and in his first game against his former team, the Chicago Cubs, LeMahieu registered three hits in four at bats.
Later in August, LeMahieu wrote his name into the record books, as he recorded 12 assists in a 9-inning victory against the Los Angeles Dodgers on the 28th.
This mark tied a record held by several players.

In 2014, LeMahieu batted .267/.315/.348 with five home runs in 494 at bats.
Defensively, he had an ultimate zone rating of 11.0, which was first in the National League (NL) and third in the majors.
He won his first Gold Glove with 16 Defensive Runs Saved and led the majors with 99 double plays.

LeMahieu was the starting second baseman for the NL in the 2015 All-Star Game; this was LeMahieu's first All-Star selection.
For the season, he batted .301 and led the majors in percentage of balls hit to the opposite field (39.0%), while seeing the highest percentage of fastballs of all MLB hitters (66.9%).

In 2016, LeMahieu won the NL batting title after batting .439 in August and .363 in September.
His .348 season average led all of MLB.
For the season, he had the highest batting average on balls in play (.388) of all major league players, and again led the majors in percentage of balls hit to the opposite field (37.9%).

LeMahieu was selected to the 2017 MLB All-Star Game as an injury replacement for Dee Gordon.
He batted .310 and for the third consecutive year led the majors in percentage of balls hit to the opposite field (38.3%), while seeing the highest percentage of fastballs of all MLB hitters (67.0%).
Also again in 2017, LeMahieu collected the NL Gold Glove for second basemen.
Additionally, he won the Fielding Bible Award for all major league second basemen.

In the 2018 season, LeMahieu hit a career-high 15 home runs while batting .276/.321/.428.
He was tied for seeing the highest percentage of fastballs of all MLB hitters (63.6%).
In addition to an increase in power numbers, his defensive excellence continued.
LeMahieu finished the 2018 season with a 19.5 SDI (SABR Defensive Index) highest of all NL players, and his 2.2 defensive WAR was eighth best among all of MLB.
The .993 fielding percentage, .859 zone rating and 18 defensive runs saved were best for all NL second basemen.
He earned both a third Gold Glove and a third Wilson Defensive Player of the Year Award.
On December 8, 2011, the Cubs traded LeMahieu and Tyler Colvin to the Colorado Rockies for Casey Weathers and Ian Stewart. He began the 2012 season with the Colorado Springs Sky Sox of the PCL.
On May 23, 2012, LeMahieu was called up to the major leagues to replace injured Jonathan Herrera as a utility infielder. He returned to Colorado Springs when Herrera was activated, and was recalled to the Rockies on July 17 when Chris Nelson was hospitalized. On August 14, he recorded a career-best four hits in a 9–6 Rockies win over the Milwaukee Brewers and in his first game against his former team, the Chicago Cubs, LeMahieu registered three hits in four at bats. Later in August, LeMahieu wrote his name into the record books, as he recorded 12 assists in a 9-inning victory against the Los Angeles Dodgers on the 28th. This mark tied a record held by several players.
In 2014, LeMahieu batted .267/.315/.348 with five home runs in 494 at bats. Defensively, he had an ultimate zone rating of 11.0, which was first in the National League (NL) and third in the majors. He won his first Gold Glove with 16 Defensive Runs Saved and led the majors with 99 double plays.
LeMahieu was the starting second baseman for the NL in the 2015 All-Star Game; this was LeMahieu's first All-Star selection. For the season, he batted .301 and led the majors in percentage of balls hit to the opposite field (39.0%), while seeing the highest percentage of fastballs of all MLB hitters (66.9%).
In 2016, LeMahieu won the NL batting title after batting .439 in August and .363 in September. His .348 season average led all of MLB. For the season, he had the highest batting average on balls in play (.388) of all major league players, and again led the majors in percentage of balls hit to the opposite field (37.9%).
LeMahieu was selected to the 2017 MLB All-Star Game as an injury replacement for Dee Gordon. He batted .310 and for the third consecutive year led the majors in percentage of balls hit to the opposite field (38.3%), while seeing the highest percentage of fastballs of all MLB hitters (67.0%). Also again in 2017, LeMahieu collected the NL Gold Glove for second basemen. Additionally, he won the Fielding Bible Award for all major league second basemen.
In the 2018 season, LeMahieu hit a career-high 15 home runs while batting .276/.321/.428. He was tied for seeing the highest percentage of fastballs of all MLB hitters (63.6%). In addition to an increase in power numbers, his defensive excellence continued. LeMahieu finished the 2018 season with a 19.5 SDI (SABR Defensive Index) highest of all NL players, and his 2.2 defensive WAR was eighth best among all of MLB. The .993 fielding percentage, .859 zone rating and 18 defensive runs saved were best for all NL second basemen. He earned both a third Gold Glove and a third Wilson Defensive Player of the Year Award.
DJ LeMahieu