The Arizona Cardinals selected Reddick in the first round (13th overall) of the 2017 NFL Draft. He was the first linebacker selected in 2017 and one of three Temple players, along with Dion Dawkins and Nate Hairston. Reddick also surpassed Paul Palmer to become Temple's second highest draft pick in history, being only behind John Rienstra who was selected by the Pittsburgh Steelers with the ninth overall pick in the 1986 NFL Draft.
On June 8, 2017, the Arizona Cardinals signed Haason Reddick to a fully guaranteed $13.4 million contract (duration four-year), with a confirmed $7.94 Million signing bonus.
He made his professional regular season debut and first career start in the Arizona Cardinals' season-opener at the Detroit Lions and recorded a season-high eight combined tackles in their 35-23 loss. Reddick earned the start after Bucannon was declared inactive due to an ankle injury. His first career tackle came on the Lions' first drive as he tackled Lions' running back Ameer Abdullah after a five-yard run in the first quarter. The following week, he collected seven combined tackles in the Cardinals' 16-13 win against the Indianapolis Colts. On November 5, 2017, Reddick was ejected for being involved in a skirmish with Carlos Hyde and finished the game with one solo tackle and a half a sack during their 20-10 victory over the San Francisco 49ers. He made his first career sack with Olsen Pierre, tackling quarterback C. J. Beathard in the first quarter. On November 10, Reddick was fined $9,115 for his role in the brawl. During a Week 14 matchup against the Tennessee Titans, Reddick made three combined tackles and made the first solo sack of his career on quarterback Marcus Mariota as the Cardinals' achieved a 12-7 victory.