At the 2012 Summer Olympics, de Beer was part of the South African team in the 4 x 400 metres relay semifinal, where he was to run the final leg. In the second leg Ofentse Mogawane collided with Kenya's Vincent Mumo Kiilu, resulting in South Africa's withdrawal from the race. South Africa was passed into the final on appeal to the IAAF, due to interference from the Kenyan athlete who downed Mogawane. They were assigned the 9th lane. He ran the second leg in the final in which South Africa finished eighth.