The victory was an encouraging start to South Africa's preparations for the 2027 U-23 Africa Cup of Nations qualifiers and the 2028 Los Angeles Olympic Games.
Algeria take lead before half-time
South Africa dominated large portions of the opening half and created several opportunities, but the hosts were unable to convert their chances.
Algeria punished that profligacy shortly before half-time when Yanis Senhadji found the net to put the visitors 1-0 ahead.
South Africa therefore went into the break behind despite having created the better opportunities during the opening period.
Substitutes inspire remarkable comeback
South Africa made changes at the start of the second half, introducing Quwan Plaatjies and Nhlanhla Gasa.
The substitutions immediately changed the momentum of the match.
Plaatjies levelled the score in the 49th minute after combining with Gasa, before Gasa completed the turnaround five minutes later to put South Africa 2-1 ahead.
The hosts continued to threaten Algeria and eventually added a third goal through another substitute.
Faiz Abrahams produced a low finish from outside the penalty area in the 73rd minute to seal a 3-1 victory for South Africa.
Mdaka's side building towards qualifiers
The result gives South Africa valuable preparation ahead of their next competitive assignment.
The U-23 side are scheduled to face Madagascar in the next round of qualifying for the 2027 U-23 AFCON after Comoros withdrew from the competition. The tournament is also part of the pathway towards the 2028 Olympic Games.
South Africa's technical team nevertheless acknowledged that there are areas requiring improvement, particularly their finishing and defensive understanding.
The two nations are scheduled to meet again in Bloemfontein on Sunday in the second of their two international friendlies.
Match summary
• South Africa U23: Quwan Plaatjies 49', Nhlanhla Gasa 54', Faiz Abrahams 73'
• Algeria U23: Yanis Senhadji 45'
South Africa U23 3-1 Algeria U23