"The ANCYL is delirious with happiness over the silver medal won by our heroine, Caster Mokgadi Semenya," the league said in a statement issued only minutes after the race was finished on Saturday night.
The league took credit for supporting Semenya in the aftermath of her 2009 World Championship victory and ensuing controversy.
"We are immensely proud of Caster and we know she deserves the medal not only because of her tenacious and unbreakable spirit but because of the trials and triumphs she has faced and emerged victorious over," the statement read.
Semenya bagged South Africa's sixth medal at the Olympic Games when she finished second in the women's 800m final on Saturday night, making it SA's most successful appearance since readmission to international sport.
The 21-year-old's silver added to those of swimmers Chad le Clos and Cameron van der Burgh, the men's coxless lightweight fours rowing team and Bridgitte Hartley in the canoe sprint.
Semenya finished second behind Russia's Mariya Savinova (1:56.19) in a time of one minute, 57.23 seconds (1:57.23), running her best race of the season.
The third place went to Ekaterina Poistogova of Russia who finished in 1:57.53.
Meanwhile, South Africa's cyclist Candice Neethling finished 30th of 30 riders in the women's cross country final.
Neethling finished in a time of one hour, 45 minutes and three seconds (1:45:03), 14.11 minutes behind French rider Julie Bresset, who finished in a time of one hour, 30 minutes and 52 seconds (1:30:52).
Germany's Sabine Spitz finished second (1:31:54), ahead of United States rider Georgia Gould (1:32:00), who bagged the bronze medal.
South Africa's men's hockey team ended their London Olympics campaign on a high, after beating India 2-1 in the teams' 11th/12th playoff classification match at the Riverbank Arena.
The win sees them finish 11th overall, lifting themselves off the bottom of the pecking order and restoring some pride in the national side as they defeated India for the first time in a major international tournament.
South Africa suffered a poor campaign, after finishing with a single point, after playing to a 2-2 draw with Great Britain in their second match of pool A, but losing four fixtures in their pool.
Marc Mundell finished 32nd out of 51 athletes in the men's 50km race walk at The Mall in London, setting a new African record in the process.
Mundell finished in a time of three hours, 55 minutes and 32 seconds (3:55:32), 19 minutes and 33 seconds slower than Russian winner Sergey Kirdyapkin, who set a new Olympic record with his time of 3:35:59.
Australia's Jared Tallent (3:36:53) finished second, ahead of China's Tianfeng Si (3:37:16), who claimed the bronze medal.
Mundell was the only African athlete to take part in the race. – Sapa