The Ghanaian goalkeeper has linked up with the Brazilians on their pre-season camp in Rustenburg after penning a five-year contract with the African champions.
Brimah faces stern competition for game-time in Tshwane from Ugandan star Denis Onyango, Zambia's Kennedy Mweene and Thela Ngobeni, but the 30-year-old is up for the challenge.
“I am proud to have joined the African champions, and look forward to being part of the team that defends the title,” Brimah is quoted as saying on Downs's website.
“I know that Sundowns is a team that wants to win trophies, and I hope to be able to help the team achieve this.
“I am here to bring my experience, and look forward to showing the coach what I am capable of, and that I am good enough to be here. I need to convince the coach that I am good and he will decide who to field.”
Brimah insists he has great respect for Onyango, the current number one at Chloorkop.
He added: “He is great, and I want to compete with the best. That is how you grow.”
Brimah, who has AFCON experience and has plied his trade in Spain, Portugal and Germany, will be registered to play in the CAF Champions League.