The hosts almost took the lead in the opening minute but Gaston Sirino failed to find the target with a wayward shot.
There was to be another opportunity for Downs when Bangaly Soumahoro controlled Percy Tau’s pin-point cross in the box, only for the Horoya defence to stop him in time and hoof away the danger.
The first shot on target came on 11 minutes when Khama Billiat went past a few defenders to draw a save from Khadim N’diaye.
Horoya arguably got the best chance in on 20 minutes following a glancing header from Dauda Camara, which forced Razak Brimah to a save at his near post.
Horoya enjoyed a good spell at this point and Brimah had to make another save off a shot from Seyei Baffour on 26 minutes.
Towards half-time, chances continued to filter through for the hosts but they continued to fire blanks as the half ended scoreless.
Ocansey Mandela showed astounding on-the-ball qualities to produce the first chance of the second half, which came off the post minutes from the break.
The diminutive forward made amends on 52 minutes as he got ahead of Soumahoro to convert from close range for the game’s first goal.
With Downs battling to find any rhythm, the best chance they had in a 20-minute spell was spurned by Khama Billiat, who blasted over the top after breaking the offside trap.
The Zimbabwean made up for that miss later on, though, after good work from Percy Tau set him up to easily tap home the equaliser on 69 minutes.
Soon after, a brilliant pass from Sirino set-up Billiat, who controlled well before being brought down by Ndiaye to earn a penalty on 76 minutes.
It allowed Sirino the opportunity with his second goal for the club, and he obliged with a well-taken finish from 12 yards.
However, the lead was spurned later on when Aboubacar Camara found the equaliser off the head following a corner on 83 minutes for a share of the spoils in Conakry.
Horoya: N'Diaye, Assoko, Camara, Camara, Camara, Camara, Sebe Baffour, Mando, Camara, Mandela.
Sundowns: Brimah, Langerman, Arendse, Ngcongca, Soumahoro, Kekana, Mabunda, Sirino, Vilakazi, Billiat, Tau.
Subs: Mweene, Manyisa, Zwane, Brockie, Madisha, Zulu, Morena.