The 30-year-old De Jager, seeking a first European Tour success, hit four birdies in a blemish-free 67 to join Atwal on 13 under par after 54 holes.
The Indian had carded a course-record 62 in Thursday’s first round not long after completing a 16-hour journey to Mauritius and shot 68 in the third round.
Dylan Frittelli of South Africa and Miguel Tabuena from the Philippines were a stroke back in third place.
South Africa's former British Open champion Louis Oosthuizen was in a group of 16 players within five strokes of the leaders.
(Reporting by Mark Gleeson in Cape Town; Editing by Ed Osmond)