Boro have announced Pulis as the club's new manager, declaring they saw off "strong interest" to land the 59-year-old.
Former Stoke and West Brom boss Pulis takes charge at the Riverside in a bid to bolster the club's stalling promotion push.
Middlesbrough host Bolton on Boxing Day, currently sitting outside the Championship play-off places.
Pulis said, “I wanted a challenge - a real challenge - and this reminds me so much of Stoke when I went there with Peter Coates. Steve Gibson is a football man who understands the game. I have great respect for him as a person and an owner.
“I really am looking forward to this. The immediate challenge is finding out about the football club and as a team we have to get as many points as can, as quickly as we can.
“I wanted to come at this time because we have so many games in a short space of time, and I can assess everything."