Pulis arrives as the replacement for Garry Monk, who was sacked on Saturday in the wake of the 2-1 win at Sheffield Wednesday.
The 60-year-old is back in the game less than two months after being axed by West Brom.
Pulis has not managed in the Championship since guiding Stoke to promotion in 2008.
He said: “I wanted a challenge – a real challenge – and this reminds me so much of Stoke when I went there with Peter Coates. [Owner] 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.”
Middlesbrough chief Gibson moved quickly to appoint Pulis.
He identified the former Baggies boss as the ideal replacement for Monk, due to concerns over the latter’s playing style.
“We’re delighted to appoint Tony as our new manager,” Gibson said. “His experience and knowledge speaks for itself and he has a tremendous track record.
“We’re excited by this appointment and by what Tony can bring to this football club. There was strong interest from two other clubs, and we’re delighted Tony has decided to join us.
“There’s no disguising that 2017 has not been a happy year for any of us, but we’ve refocused and we’re looking forward to the future.”
Pulis will not take charge of Boro for today’s game against Bolton (3pm).