Van der Westhuizen was part of the team that won South Africa's first Tri-Nations series title in 1998. He captained the Bulls to the 1998 Currie Cup. He first captained the South Africa team in 1999. That year South Africa finished third at the World Cup. After the tournament he discovered he had sustained a serious injury to ligaments in his knee in a match a fortnight earlier. Injuries sustained while on international duty led to him missing the greater parts of three consecutive Super 12 seasons in 1998, 1999 and 2000.