The 27-year-old Victoria's Secret model, shared the news on Instagram posting a photo of her baby bump.
Agora e #barrigapositiva ! #babybump," she wrote. She later changed the last hashtag to #babyangel.
Swanepoel and Nicoli got engaged in August 2015. The South African model showcased her engagement ring weeks later.
The couple have been together for about a decade and first met in Paris when she was about 17.