Beasley went undrafted in the 2012 NFL Draft because of his size and was signed by the Dallas Cowboys. He left abruptly during training camp, stating he was dealing with “personal stuff”, and even considered retiring from professional football. He went on to have a sudden change of heart, returning and making the final 53-man roster. As a rookie, he appeared in ten games and made 15 receptions for 128 receiving yards.

Beasley posted career highs in receptions and yards, catching 75 passes for 833 yards and five touchdowns on 98 targets. His 76.5% catch rate ranked second among NFL wide receivers in 2016.

In the 2017 season, Beasley finished with 36 receptions for 314 receiving yards and four receiving touchdowns.

Beasley released the debut single release “80 Stings” in 2017. In 2018, he released his debut album The Autobiography produced by Victor “Phazz” Clark. The two teamed up to form ColdNation Records an independent record label located in Frisco, Texas.

Beasley started the 2018 season with seven receptions for 73 yards in a 16–8 loss to the Carolina Panthers. In Week 6, against the Jacksonville Jaguars, he had nine receptions for 101 yards and two touchdowns in the 40–7 victory. Overall, he finished with 65 receptions for 672 yards and three touchdowns in the 2018 season. The Cowboys won the NFC East and earned the #4-seed in the NFC Playoffs. In the Wild Card Round against the Seattle Seahawks, Beasley had three receptions for 28 yards in the 24–22 victory. In the Divisional Round against the Los Angeles Rams, he had one reception for 15 yards in the 30–22 loss.

On March 13, 2019, Beasley signed a four-year, $29 million contract with the Buffalo Bills. Beasley caught his first touchdown reception with the Bills in a 31–21 Week 6 win over the Miami Dolphins. Against the Dallas Cowboys, his former team, on Thanksgiving Day in Week 13, Beasley finished with 110 receiving yards and a touchdown as the Bills won 26–15. In Week 16 against the New England Patriots, Beasley caught seven passes for 108 yards during the 24–17 loss. Overall, Beasley finished the 2019 season with 67 receptions for 778 receiving yards and six receiving touchdowns.

Beasley was placed on the active/non-football injury list at the start of training camp on July 29, 2020. He was moved back to the active roster on August 12.