The Irish led 13-3 at the break and managed to score a try in each half, whereas South Africa relied heavily on the boot of flyhalf Tony Jantjies to keep their hopes of victory alive on Monday.
The Baby Boks started off as if they would take Ireland apart with strong ball carries and their physical approach seemingly giving them the edge.
They secured territorial advantage but did not translate it to points and after camping in the Irish 22-metre area for some six minutes they had only a single Jantjies penalty, in the 11th minute, to show for their efforts (3-0).
After Ireland had held out on defence, they broke out with effect as the pressure they exerted saw the Baby Boks infringe at the breakdown.
In the space of nine minutes flyhalf JJ Hanrahan was twice on target with penalties from 30 metres out, which allowed the visitors to take the lead for the first time in the match.
As it turned out, the Irish never again relinquished the lead in the half as the Boks lost their rhythm.
Some 10 minutes ahead of the break the 12 000-strong crowd went silent as South Africa suffered another setback when openside flanker Jordon Coglan romped in for the first try of the match.
Hanrahan added the conversion from the touchline to open up a commanding 13-3 lead, which they held till half-time.
The Baby Boks were off to a sluggish start in the second period but they soon turned that around and the Irish try line was under siege eight minutes after the break.
The pressure took its toll as lock Paul Willemse crashed over for a converted try and the score seemed to lift the Boks’ play considerably in the ensuing minutes.
The Irish managed to sneak into the South African half when they looked under the whip and Hanrahan snapped over a drop goal to open up a six-point lead.
Jantjies was twice on target with long-range penalty attempts and with 16 minutes left the scores were level at 16-all.
But nine minutes before the final whistle, flanker Conor Gilsenan rounded off a great driving maul with a converted to put Ireland back on top.
A late Jantjies penalty could not change South Africa’s fate.
Scorers: South Africa: Try: Paul Willemse. Conversion: Tony Jantjies. Penalties: Jantjies (4).
Ireland: Tries: Jordon Coglan, Conor Gilsenan. Conversions: JJ Hanrahan (2). Penalties: Hanrahan (2). Drop goal: Hanrahan. – Sapa