[6] A low three-star prospect, ranked by 247Sports as the nation's 308th best wide receiver coming out of high school, he committed to Louisiana State University (LSU) to play college football.

[28] The Vikings previously obtained the 22nd selection as part of a blockbuster trade that sent wide receiver Stefon Diggs to the Buffalo Bills, a trade that has been considered by many around the league as one of the “top win-win deals ever.”[29][30] Jefferson signed a four-year, $13.12 million contract with the team, with a $7.1 million signing bonus.

[34] He made his first start of the season in a Week 3 game against the Tennessee Titans, where he had his first big breakthrough by finishing with 175 receiving yards and a touchdown on seven receptions, but the Vikings lost 31–30.

[40] He was one of only two rookies named to the 2021 Pro Bowl, alongside defensive end Chase Young of the Washington Football Team.

[52][53] For the second consecutive year, Jefferson was named a second-team member of the AP All-Pro team, missing a spot on the first-team by a single vote.

[56] During Week 4 against the New Orleans Saints at Tottenham Hotspur Stadium, Jefferson finished with 147 receiving yards and a rushing touchdown as the Vikings won 28–25.

[59] Against the Buffalo Bills in Week 10, Jefferson caught 10 passes for a career-high 193 yards and a touchdown as the Vikings went on to win 33–30 in overtime.

His arm sleeves and gloves from the game were also put on display in the Pro Football Hall of Fame.

[68] Against the Packers in Week 17, he was held to one catch on five targets for 15 yards, the lowest stats in a game of his career.

During the same game, Jefferson appeared to inadvertently hit a referee with his helmet out of clear frustration, and received no punishment for the incident.

[71][72] Jefferson finished the 2022 regular season with a league-leading 128 receptions for 1,809 yards and nine total touchdowns (eight receiving, one rushing).

[77] Jefferson started the 2023 regular season with nine receptions for 150 yards in a 20–17 loss to the Tampa Bay Buccaneers in Week 1.

[81] On October 11, 2023, the Vikings placed Jefferson on injured reserve, due to a hamstring injury suffered in Week 5 against the Kansas City Chiefs.

[83] In his return against the Las Vegas Raiders in Week 14, Jefferson caught two passes for 27 yards before leaving with a chest injury in the second quarter.

[88] In Week 2, Jefferson caught a 97-yard touchdown pass and achieved 400 career receptions in a 23–17 win over the San Francisco 49ers.

He also tied Lance Alworth for the fastest player in NFL history to achieve 6,000 career receiving yards, doing so in 62 games.

[89] In Week 11 against the Tennessee Titans, Jefferson passed Torry Holt for the most receiving yards in a player's first five NFL seasons.

[91] After a career-long six game touchdown drought, Jefferson had his first multi-touchdown performance of the season in Week 14 against the Atlanta Falcons, finishing with 132 yards and two scores in a 42–21 victory.