The 27-year-old South African is making only his 16th start at this level and currently sits in 19th place on the Sunshine Tour as he carded seven birdies through 12 holes to climb to the top of the leaderboard at Houghton Golf Course.
Brown missed the cut at last week's South African Open Championship, but he had recorded four successive top-ten finishes prior to the Stellenbosch event, including third at the Jonsson Workwear Durban Open in February.
He heads the field by one at seven under par, but Brown could play up to 24 holes on Friday, which has a bleak forecast, following a weather delay of an hour and 45 minutes due to thunder and lightning in the area during the first round.
Brown got off to a fast start with an opening birdie at the tenth and he continue his charge with further gains at the 12th, 15th and 17th to reach the turn in 31.
He was only two off the pace set by fellow South African Jayden Schaper, Englishman Nathan Kimsey and Austria's Maximilian Steinlechner at six under, but a hat-trick of birdies from the first saw him nudge ahead before play was suspended at 6.17pm local time due to darkness.
Two-time DP World Tour winner Schaper made a fast start with an opening birdie at the tenth and then rolled in another at the 17th. A third birdie of the day arrived at the first and he reached four under with a gain at the fourth.
He soon climbed to the top on his own when he found the par-five in two and when Schaper drained the 15-foot eagle putt, he was at six under following his flawless 64.
"On this golf course it is always nice to go bogey-free, especially on the first day and get off to a nice start," Schaper said.
"You always look forward to the second day and the rest of the week after a start like that, but I guess you have to wait to see what the weather has planned for us."
That set the clubhouse target and it was matched by Kimsey, who was the first reserve and only found out he was in the field at a few minutes' notice.
His group were already down the tenth fairway - their first hole - and the Englishman was made to catch up, but he did not hang around as he went birdie-bogey-birdie from the 11th.
A birdie at the 16th saw Kimsey reach the turn in 33 before improving further with gains at the fourth, sixth, seventh and ninth to join Schaper in a share of the lead at six under.
"In the circumstances, it was fantastic. I mean I couldn't have asked for any more," Kimsey said.
"Six hours ago I didn't have a tee-time so it was nice to get out there and play some good golf and I'm pleased to be part of the tournament, and looking forward to the next few days."
Steinlechner rolled in a birdie at the last, his seventh of the day to go with a bogey, to reach six under, while Spaniard Angel Ayora signed for an eagle and four birdies to get to that mark through 15 holes and is one of 54 players yet to finish their first rounds.
Denmark's Jacob Skov Olesen recorded his lowest first round of the season in his 65 to sit alongside home hopeful Wilco Nienaber, Dutchman Darius van Driel and Sweden's Hugo Townsend at five under. Dan Bradbury and Kieran Vincent are also at that mark with four and eight holes to play of their opening rounds respectively.
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