Okafor signed with Duke as a package with Tyus Jones, with widespread recognition as the preseason Collegiate National Player of the Year.

[4][5] His father, Chukwudi, known as Chuck, is a second-generation Nigerian American of Igbo descent, and his mother, Dacresha Lanett Benton, was Bantu-American and European-American.

[11] Initially, interim coach Tracy Webster, made an oral offer on January 30 outside the DePaul locker room at Allstate Arena.

[9][12] In February 2010, Ponsetto confirmed in a statement: This is a young guy we've been talking with for a long time, and who has been to games and we have a relationship with because his uncle works for the Rosemont Police Department...I think it's a prospect who has grown up around DePaul basketball.

[14] Along with 6 ft 10 in (2.08 m) sophomore Thomas Hamilton Jr. and White, Okafor was part of a trio of Whitney Young players ranked in the top 10 of their respective national classes by ESPNU.

[17] The scouting report on him was that he possessed an improved mid-range jump shot, nimble feet, soft hands and physical skills at 6-foot-9-inch (2.06 m) that made him a mismatch against almost any high school competitor.

[21] On December 22, in front of an audience that included John Calipari, Rick Pitino, Derrick Rose and Anthony Davis at the UIC Pavilion, Okafor had 20 points (10 in the fourth quarter), nine rebounds and three blocked shots against cross-town rival Simeon and its star Parker in a 62–55 loss.

[22] Following the season, the Chicago Sun-Times named him to the Class 4A All-State first team along with Parker, Keith Carter, Darius Paul and Fred VanVleet.

[34] Okafor was named as one of the top 5 Illinois Mr. Basketball contenders (along with Parker, Kendrick Nunn, Sterling Brown and Malcolm Hill) prior to the season by the Chicago Tribune's Mike Helfgot.

[38] On January 19, Okafor led Young to an 85–52 victory over Long Beach Polytechnic High School at the Hoophall Classic with 26 points, 7 rebounds and 3 blocks.

[40] In the Chicago Public High School League playoffs February 15 finals contest against Morgan Park High School Okafor tallied 19 points, 14 rebounds and 7 blocked shots, including a game-saving block against Billy Garrett Jr., in a 60–56 overtime Public League Championship game victory over Morgan Park.

[48] Following his time with Team USA, Okafor participated in the Nike Pro-Am Chi-League,[49] the All-Peach Jam,[50] and the Adidas Nations event.

[52] Prior to his senior season, USA Today named him to its 10-man preseason All-USA team along with Alexander, Stanley Johnson, Jones, Trey Lyles, Mudiay, Malik Newman, Kelly Oubre, D'Angelo Russell, and Myles Turner.

[54] Okafor was joined on the Chicago Tribune's preseason Illinois Mr. Basketball top 5 by Alexander, Jalen Brunson, Tyler Ulis and Keita Bates-Diop.

[55] Okafor dominated the December 27–30, Les Schwab Invitational hosted by Liberty High School by leading the tournament in scoring (31) and rebounding (12.5) and finished 2013 atop the three major recruiting databases (ESPN, Rivals and Scout).

[58] On January 4 at the Cancer Research Classic in Wheeling, West Virginia, Okafor earned the tournament MVP based on a 24-point and nine-rebound performance against Mudiay's Prime Prep Academy.

[59] Okafor and Young reached an anticipated city championship matchup with Curie and Alexander at the Jones Convocation Center.

[61] The CPL Championship game was attended by Mayor of Chicago Rahm Emanuel and was the lead story on the late edition of SportsCenter.

[64] On March 21 Okafor's 33 points and 14 rebounds enabled Young to overcome a record setting 56-point performance by Brunson with a 75–68 victory over Stevenson High School.

[66] Okafor earned co-MVP (with Justin Jackson) of the April 2, 2014, McDonald's All-American Game after posting 17 points and 7 rebounds, including the go ahead dunk with fewer than 40 seconds remaining,[67] for the winning west team in a 105–102 victory.

He was recognized as first team All-City along with teammate White, Alexander, Louis Adams Jr. of Orr, and Luwane Pipkins of Bogan High School by the Chicago Sun-Times.

[75] USA Today recognized Okafor as its national player of the year when naming its All-USA Boys Basketball Team along with Alexander, Oubre, Mudiay, and Stanley Johnson.

[118] After sitting out a game due to an ankle injury, Okafor posted a career-high 30 points in an overtime win against Virginia Tech on February 25.

[147] On February 28, Okafor posted 26 points against the Orlando Magic,[148] but he endured a shin contusion in a collision with teammate Isaiah Canaan that was only expected to sideline him for a game.

[151] On March 11, Okafor was ruled out for the rest of the season after tests revealed that he had sustained a small tear of the meniscus in his right knee.

[155] Okafor began the season on a 16-minute cap to be played over "smaller segments" and restriction from back-to-back game participation following the re-aggravation of his meniscus injury.

[169][170] On December 7, 2017, Okafor was traded, along with Nik Stauskas and a 2019 second round draft pick, to the Brooklyn Nets in exchange for Trevor Booker.

[199] On February 4, 2023, Okafor's rights were traded, along with Shabazz Napier, Bruno Caboclo, and Matt Mooney to the Delaware Blue Coats in exchange for Skylar Mays, Justin Robinson, and Raphiael Putney.

[222] On February 23, 2020, Jahlil Okafor told ESPN's Marc J. Spears that he would represent the Nigeria national team at the 2020 Summer Olympics.

[225] His mother, Dacresha Lanett Benton,[7] died when he was nine years old, leaving him to be raised by his father Chukwudi and aunt Chinyere Okafor-Conley,[9] whom he refers to as his "auntie mom".