The England goalkeeper was full of praise for the 19-year-old Arsenal star, who came off the bench to fire the visitors level at the new Maracana Stadium in Sunday's 2-2 draw
Fred put the hosts ahead in the second half but substitute Oxlade-Chamberlain smashed in from outside the box to equalise for the Three Lions.
Wayne Rooney then sent England in front with a deflected effort off Paulinho before the Samba midfielder equalised moments later, but Hart was full of praise for the Arsenal youngster.
"He [Oxlade-Chamberlain] ripped it up [after coming on]," he told ITV Sport.
"You look at all the Brazil players and there's a lot of focus on their players, then 'the Ox', 19 years old comes on and smashes us back in the game. You can't ask for much more."
Hart also spoke about Rooney's strike that had put the Three Lions ahead before lamenting his side's poor first-half performance.
On the Manchester United striker's goal, he said: Yeah, brilliant. A bit of spin on it, a deflection, but we dug deep.
"It wasn't how we wanted to play first half, we can moan all we want about the heat and the end of a long season, it's our last game and they were coming into it sharp, trying to play well. The likes of 'the Ox' came on and it was good for Jack [Rodwell] as well."