Born in Welkom, de Beer represented Northern Free State at the 1989 Craven Week tournament. He made his senior provincial debut for the Free State in 1990 as a 19-year-old.
De Beer made his début against the British & Irish Lions in 1997, being brought in for the dropped Henry Honiball whose running game had been contained by the Lions' defence in the first two of the three tests. He failed however to establish himself properly in the Springbok side.
De Beer is most famous for his world record five drop goals in a single test match, set in the 1999 Rugby World Cup in Paris against England. The Springboks won the match 44-21, knocking England out of the tournament. However, his attempts to repeat the tactic in the semi-final versus Australia backfired, as despite several attempts he only scored one in the match, and the Australians closed him down. It proved to be his final appearance for the Springboks.
De Beer retired from professional rugby in 2002 due to a knee injury.
At the end of 2019, de Beer was appointed as the director of rugby at the Windhoek Gymnasium.