NPA spokesperson Natasha Ramkisson-Kara said Nyawose was convicted in the Port Shepstone Magistrate's Court on Friday by Magistrate Charmaine Barnard.
Stander, 25, died on January 3, 2013 when he was struck while cycling in Shelley Beach on the KwaZulu-Natal South Coast.
He was fifth in the men's cross-country race at the 2012 London Olympics. Four years earlier, at the Beijing Games, he finished 15th in the cross-country event.
In 2011, Stander became the first South African to win the Cape Epic stage race in the Western Cape with Swiss partner Christoph Sauser. The pair defended their title in 2012.
It was not immediately clear when Nyawose would be sentenced.
News24