The Brazilians dominated for most of the match and should have won by a much bigger margin, was it not for their poor finishing in front of goal.
Trott Moloto’s side took the lead in the seventh minute when Moriri headed home a cross by Siboniso Gaxa.
Celtic dominated midway through the first half, but failed to seriously trouble the Sundowns defence.
The visitors came back strong towards the end of the half, with Fanyana Dhladhla forcing Celtic keeper Shuaib Walters into a good save in the 41st minute, while Mbulelo Mabizela hit the crossbar seconds before the break following Celtic’s failure to clear a corner by Josta Dladla.
The score remained 1-0 at the break, with Sundowns continuing in the same vein in the second stanza.
Shakes Ngwenya should have doubled the visitors’ lead in the 54th minute when he latched onto a good cross by Moriri, but the striker put his effort wide at the near post.
The game was disrupted as both sides rang the changes, although Celtic could have stolen a point at the end when Baloyi failed to collect a cross, but substitute Mayambela put his header wide of the empty goal.