Westwood will be joining fellow Englandman Justin Rose and South Africa's Trevor Immelman in the field for the European Tour's first event in 2003.
The season officially got under way with the BMW Open in late November and the Hong Kong Open the following week.
Westwood is hoping the sunny, warm weather in South Africa will help him get off to a good start for 2003 after two lackluster seasons.
Westwood was sitting atop the European Tour in 2000 after winning seven titles and wresting away the Volvo Order of Merit crown Colin Montgomerie had held for almost a decade.
But since then he has fallen from the top of the European Order of Merit all the way down to the 75th spot in 2002.
The field for the South African Airways Open Championship is starting to fall into place as more and more top international golfers confirm their participation in this prestigious tournament, said Louis Martin, the Chief Executive of the Sunshine Tour.
Lee has long been a supporter of the Tour and it will be wonderful to have a player of his calibre teeing it up at Erinvale.