Kara Mbodji earned Alain Giresse's side a point on Friday with a stunning header on the hour, moving them above Algeria and onto four points.
South Africa had threatened early in the match, but lacked quality in front of goal, while Mame Biram Diouf wasted Senegal's best chance.
Oupa Manyisa's composed finish sparked the game into life early in the second half, with Sadio Mane having an equaliser disallowed before Mbodji brought Senegal level on the hour.
Moussa Sow and Diouf both had chances to win it for Senegal, but they had to settle for a point that puts them in pole position to qualify from the group.
For South Africa, they need to beat Ghana on Tuesday and hope Senegal can take all three points against Algeria if they are to reach the last eight.
Shakes Mashaba's side started well and went close in the 11th minute through Sibusiso Vilakazi, the forward playing a neat one-two before unleashing a vicious drive that Bouna Coundoul was able to push away.
With 25 minutes gone, Senegal tested Jackson Mabokgwane for the first time as midfielder Papakouli Diop went for goal from 30 yards, but his free-kick was easily gathered by the goalkeeper.
Diouf was presented with the clearest opening of the half with half-time approaching from a left-wing corner, but the Stoke City forward placed his header wide.
Senegal were made to rue those misses as South Africa began the second half with renewed intent and got their reward as Manyisa opened the scoring.
Anele Ngcongca made good ground down the right two minutes after the restart and his low cross evaded everyone at the front post, but Manyisa was on hand at the back to calmly slot home.
Senegal thought they were level 10 minutes later when Mabokgwane dropped Lamine Sane's header to allow Mane to score, but the Southampton forward was denied by the offside flag - albeit not against him.
It mattered little as the match was all-square three minutes later, Mbodji rising at the back post to power Diouf's free-kick into the net.
Tokelo Rantie, who had been fairly ineffective in attack for South Africa, went close to putting his side back in front after 74 minutes, but the Bournemouth striker was foiled by a superb tackle from Cheikh M'Bengue.
Substitute Dame N'Doye brought another good save out of Mabokgwane in the final 10 minutes, but Senegal needed a crucial block from Lamine Gassama to secure the point.
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