The 30-year-old former Peterborough forward has signed a two-and-a-half year deal with the club and is hoping to go straight into Phil Parkinson's squad for Saturday's derby clash at Sheffield United.
Parkinson, who has moved quickly to fill the void left by Nahki Wells, told the club's official website: "I'm thrilled by the arrival of Aaron.
"He is someone I have monitored for a while now and he has a proven record at this level.
"Aaron is a fantastic player and he will be a great personality to have around the dressing room.
"I am sure he is going to be an excellent acquisition for the football club."
McLean has had loan spells at Ipswich and Birmingham during his time at Hull, who he joined in 2010 from Peterborough.
He has appeared three times for Hull this season, including one substitute appearance in the Barclays Premier League game at Tottenham in October.
Wells, Bradford's leading goalscorer this term, departed for Huddersfield in a club-record B£1.3million deal last week.
- Sports & Recreation
- Nahki Wells
- Phil Parkinson