The former Aston Villa goalkeeper joined Boro on a free transfer last week.
Guzan joined the newly-promoted Premier League side on a free transfer from relegated Aston Villa last week after falling out of favour at Villa Park.
The American had been at Villa for eight years, serving as first-choice for the latter half of that spell, but lost his place to Mark Bunn during the later stages of last term after some inconsistent form and individual errors.
He now faces an almighty battle to establish himself as the go-to player in between the posts at the Riverside as he adds to a wealth of goalkeeping options on Teesside.
Guzan is the second stopper to sign for the club this summer after experienced and hugely successful former Barcelona mainstay Victor Valdes joined last year's number one Dimi Konstantopoulos and back-up Tomas Mejias.
The American will do well to emerge as the leader of the pack amongst that group, but has insisted that the competition will be great for him in his new surroundings.
The 31-year-old told the Boro website: "They are great goalkeepers and I’m very fortunate and happy to be part of this group. There’s a belief and truth in the goalkeepers' union for sure. You want to battle - you need competition for places and that brings the best out of players.
"There’s an understanding between goalkeepers that everyone competes day in and day out to try and be selected on a matchday. Training is quite intense, and that’s good. You need that competitiveness so that when the matchdays roll around, everyone is ready to get a good result.
"You want your name to be called and you do that by proving your worth Monday to Friday on the training field. Hopefully Saturday afternoon you can do the job, help the guys in front of you and keep the ball out of the back of the net."
Though his status within the squad will not become clear until the season is well underway, Guzan will boast the most Premier League experience of any of Boro's keepers, having played nearly 150 times in the top flight for Villa.
He will certainly be a good option to have in rotation for Aitor Karanka as the club look to ensure that they do not fall back through the trapdoor at the first time of asking.