He played college football for the Oklahoma Sooners where he was a consensus All-American in 2019, and was selected by the Cowboys in the first round of the 2020 NFL draft.

Lamb was born in Opelousas, Louisiana, and lived in New Orleans until he and his family evacuated to Houston, Texas, following Hurricane Katrina's effects on the city in 2005.

[3] Lamb, with quarterback Alex Ramart, led the team to a 14–1 overall record, with the only loss coming to Temple High School in the 5A-D1 state semifinals.

[19] Lamb had a career-high eight receptions for 109 yards and one touchdown against the top ranked Alabama Crimson Tide in the College Football Playoff semifinal at the 2018 Orange Bowl.

[22] Lamb was named the Most Outstanding Player of the Big 12 Championship, after collecting 173 yards on eight receptions (including a 71-yarder that set up the team's first touchdown) in a 30–23 victory over #7 Baylor.

[23] He had four receptions for 119 yards (including a 51-yarder) in the College Football Playoff Semifinal at the 2019 Peach Bowl in a 63–28 loss to #1 Louisiana State University.

[29] Lamb made his NFL debut in the season-opener against the Los Angeles Rams on NBC Sunday Night Football, recording five receptions for 59 yards in the 20–17 road loss.

[33] During a Week 9 24–19 loss to the Pittsburgh Steelers, Lamb caught four passes for 71 yards and his third touchdown of the season while also losing his first fumble of his career.

[34] During a Week 15 41–33 victory over the San Francisco 49ers, Lamb recorded five catches for 85 yards and returned an onside kick attempt for a 47-yard touchdown.

In the Wild Card Round against the Tampa Bay Buccaneers, he recorded four receptions for 68 yards and his first postseason touchdown in the 31–14 road victory.

[55] After the Cowboys' Week 10 49–17 win against the New York Giants, Lamb became the first player in NFL history to have at least 10 catches for over 150 yards in three consecutive games.

[57] Entering the fifth-year option of his rookie deal, Lamb skipped voluntary workouts, mandatory minicamp and training camp, holding out for a new contract.