The famed fashion designer has been giving fans a glimpse of her trip by busily posting pictures on social media, including one shot of her showing off her artistic side while graffiting a wall of an AIDS education centre.
She captioned the picture: "Education + art = Aids free future @UNAIDS x vb."
In another shot Posh meets locals and embraces a young boy on what she tweeted was an "inspiring day".
The 40-year-old former pop star also made the time to speak with women in Soweto and sat with them on a patch of grass to hear their stories of what it's like living where they do.
The mother-of-four's maiden UN visit follows her appearance the United Nations building in New York last month, where she said she was "honoured" to have been made a representative for the UNAIDS campaign.
After the announcement was made in New York an impassioned Victoria addressed the crowd where she credited the love she has for her family for inspiring her charity work.
"I am mother and I am a woman. I will do whatever I can to raise awareness. I feel very passionate about this," she told the UN audience in New York.
"I recently visited South Africa and was so touched by the women I met and felt inspired. I came home and I knew I had to do something."
"It's taken me to get to 40 to realise I have a responsibility as a woman and as a mother. For some reason people will listen to me. This is the beginning of an incredible journey for me."
She later added: "I would do anything for my children and I think every woman has the right to health and every woman has the right to give their children a healthy future."