Competing at her first Olympics, Phumlile Ndzinisa was notable for carrying the Swaziland flag at the closing ceremony. She was the youngest person to compete for Swaziland at the Games, aged 19. She qualified for the Olympics via a wildcard, as her best time, 54.26 seconds set at the 2011 All-Africa Games, was 1.96 seconds slower than the "B" qualifying standard for the women's 400 metres. Ndzinisa took part in the first round of the women's 400 metres and was drawn in the fourth heat. She finished sixth with a time of 53.95 seconds, behind heat winner and eventual gold medallist Sanya Richards-Ross of the United States (51.78 seconds). Ndzinisa finished 36th out of 45 athletes overall, and was 1.64 seconds behind the slowest qualifier who progressed to the semi-finals and that was the end of her competition.