Halsey made his professional debut in 2012 against Chris Golz. Halsey won the bout via submission in the first round. In his second fight, Halsey faced UFC veteran Shonie Carter. Halsey won the bout via unanimous decision.
Bellator MMA
After winning his first two fights, Halsey was signed by Bellator Fighting Championships and made his debut against Rocky Ramirez at Bellator 92 on March 7, 2013. Halsey won by technical submission in the third round. Halsey fought Joe Yager at Bellator 96 on June 19, 2013 and won the bout via split decision. Halsey faced UFC veteran Hector Ramirez at Bellator 106 on November 2, 2013. Halsey won the bout via TKO in the first round after using his superior wrestling to take the fight to the ground, transition immediately to the back, and unload with punches to the head until he earned the victory.
Season Ten Middleweight Tournament winner
In March 2014, Halsey entered into the middleweight tournament when Dan Cramer versus Jeremy Kimball was cancelled. He fought Joe Pacheco at Bellator 116 on April 11, 2014. Halsey won the bout via unanimous decision. Halsey was scheduled to face Brett Cooper in the finals at on May 9, 2014. The bout, however, was delayed due to an injury sustained by Cooper. The Cooper fight took place at on July 25, 2014. Halsey won the bout via submission in the first round.
Middleweight Champion
Halsey faced Alexander Shlemenko for the Bellator Middleweight Championship on September 26, 2014 at Bellator 126. Halsey won the bout via technical submission in the first round to become the new Bellator Middleweight Champion. Halsey was expected to make his first title defense against Kendall Grove on May 15, 2015 at Bellator 137. However, Halsey failed to make weight and was subsequently stripped of the middleweight championship. Halsey won the fight via TKO in the fourth round. Halsey next faced Rafael Carvalho for the vacant Bellator Middleweight Championship on October 23, 2015 at Bellator 144. After dominating the opening round with his grappling, Halsey lost the fight via TKO in the second after absorbing a kick to the liver. Halsey faced John Salter on June 17, 2016 at Bellator 156. After sustaining an early cut via head kick, Halsey went on to lose the bout via submission in the first round. On October 5, 2016, Halsey was released from Bellator.
M-1 Global
On June 1, 2017, Halsey rematched Alexander Shlemenko at M-1 Challenge 79 and was submitted by strikes after 25 seconds of the first round, marking his third consecutive loss after starting his career 9-0. He then face Mikhail Ragozin on September 23, 2017 at M-1 Challenge 83: Ragozin vs. Halsey. He won the fight via unanimous decision.
Personal life
Halsey and his wife Amber gave birth to their first child, daughter Savannah Rose, in June 2015.