Schwartzel was joined atop the leaderboard by Phillip Archer, Wayne De Haas, Alessandro Tadini and Oliver Wilson.
Seven more players, including Andrew Coltart, are one stroke further back at minus-3. The top of the leaderboard is crowded with 37 players breaking par at Leopard Creek Country Club.
Defending champion Ernie Els is one of 16 players tied for 38th place at even-par 72 after round one. Els posted four birdies and two bogeys on his opening nine and two bogeys on his second nine.
Schwartzel flew out of the gate with birdies on three of the first four holes to move within one of Tadini's lead. Schwartzel birdied the par-4 sixth to join Tadini in first.
The 22-year-old Schwartzel stumbled to a bogey on the par-4 eighth to drop out of a share for the lead. He regained a piece of first with a birdie on No. 10. Schwartzel parred his final eight holes.
Tadini, the only of the five leaders to play in the morning group, was even-par through nine holes. However, it was an interesting opening nine with an eagle, a birdie and three bogeys.
'My long game was so-so and the difference today was my putting, which was wonderful,' Tadini stated. 'My driver was not good today, but the rough is not so bad so it was okay.'
Around the turn, Tadini dropped in back-to-back birdies from the 11th. He closed with birdies on 16 and 18 to finish at minus-4.
Archer got to 2 under with birdies on the second and sixth, but tripped to a bogey on seven. Archer moved within one of the lead with birdies on 10 and 11.
The 34-year-old stumbled to a bogey on 13, but rebounded with consecutive birdies from the 14th to get to minus-4. He closed with three straight pars.
Wilson birdied the first two holes, but faltered to a bogey at the seventh. Around the turn, he picked up three birdies in a five-hole stretch from the 11th to move to 4 under. After a bogey on 16, Wilson birdied the last to share the lead.
De Haas, who was the only of the five leaders to play the back nine first, carded the only bogey-free round of the five leaders. His birdies came at 14 and 17 on his first nine, then two and six around the turn.
Coltart was joined in sixth place at 3-under-par 69 by David Higgins, Blanche Lamprecht, Alan Michell, Steve Van Vuuren, Rafael Cabrera Bello, Simon Nash and Sam Walker.
Ten more players, including Andrew McLardy and Louis Oosthuizen, are tied for 13th at minus-2.