Ogletree and his twin brother Alexander (Zander) were born in Newnan, Georgia. He attended Newnan High School, where he played high school football and basketball and ran track for the Newnan Cougars. He was widely considered to be one of the top football prospects of the 2010 high school class. He was rated as the No. 22 recruit by Scout.com, the No. 29 recruit in the ESPNU 150, and the No. 40 player by Rivals.com.
In his sophomore season, Ogletree had six blocked punts and returned one for a touchdown. He had 75 tackles, three interceptions and six blocked punts as a junior. In his senior year, Ogletree had 85 tackles, 5 tackles for loss, 2 forced fumbles, two interceptions and two blocked kicks on defense—and he had 33 receptions for 633 yards and 5 touchdowns on offense.
Also an standout track and field athlete, Ogletree was one of the state's top performers in the long jump. He captured the state title in the long jump event at the 2010 GHSA Region 4-AAAAA track and field championships, with a PR leap of 7.30 meters (23 ft, 11 in). He also ran the 400-meter dash and was a member of the Newnan 4×100-meter relay squad.
Following his senior season in 2009, he was recognized as a high school All-American by Under Armour, USA Today, and Parade. Ogletree verbally committed to attend the University of Georgia in June 2009. He made his commitment official by signing his letter of intent to play at Georgia on February 3, 2010, choosing it over tens of other Division-1 schools including the University of Alabama, Auburn University, University of Florida, Florida State University and Georgia Tech. His brother Zander also went to UGA, playing fullback.
Ogletree received an athletic scholarship to attend the University of Georgia, where he played for coach Mark Richt's Georgia Bulldogs football team from 2010 to 2012.
In 2010, Ogletree returned from his one-game suspension and was inserted into all the special team units. He eventually started getting some small amounts of playing time at safety. He was inserted into the starting strong safety spot for the final 3 games of the regular season for Georgia.
In 2011, Ogletree broke his foot during the first quarter of Georgia's season opener vs. Boise State. He missed the following six games, returning for the Florida game on October 29. Against No. 1 LSU in the 2011 SEC Championship Game, he recorded 6 tackles including two for a loss, 1 sack and recovered a 1st quarter onside kick. In a little over 8 games, Ogletree finished the 2011 season with 52 tackles (6.5 per game) including 7.5 for a loss, 3 sacks, 2 forced fumbles and a pass deflection that was intercepted.
Ogletree was selected by the St. Louis Rams in the first round, 30th overall, of the 2013 NFL Draft with the 30th overall pick in the draft.
On October 27, 2015, the Rams placed Ogletree on injured reserve with a designation to return due to a broken fibula.
In the 2016 offseason, Ogletree was moved from weakside linebacker to inside linebacker after the release of James Laurinitis. On May 2, 2016, Ogletree along with fellow Rams teammate Tavon Austin had their fifth-year option picked up by the Los Angeles Rams. He started all 16 games and recorded a career-high 136 tackles, good for seventh in the NFL.
Alec Ogletree has a twin brother, Alexander Ogletree, who played fullback for the University of Georgia.
In September 2010, Ogletree was arrested and charged with misdemeanor theft stemming from a June incident of a stolen scooter helmet. Ogletree was suspended by Georgia for the first game of the season. In February 2013, just days before the 2013 NFL combine, Ogletree was arrested on charges of DUI in Arizona, per a statement released by his agent.