Grace, 27, put together two birdies and an eagle on his opening nine to move to three under, before two bogies coming home dropped the six-time European Tour winner to one under for the tournament.
The world-number-40 was left well-placed in a tie for 14th just four shots behind leaders Henrik Stenson of Sweden and American Dustin Johnson who both fired opening rounds of 65.
Starting on the 10th hole, Grace could be forgiven for thinking the notoriously difficult layout would not yield an under par score as he could only manage a bogey on the par four.
But Grace did not take long to strike back with an eagle on the driveable par four 12th, before birdies on 14 and 18 to get his round going.
Even with the two further drops on his way back to the clubhouse, it could not take the gloss off a fine opening round for the South African that could well stun a few Americans on Sunday.
Ernie Els and George Coetzee were the next best placed SA players with a pair of two over 72s in a share of 52nd. The Big Easy, a two-time US Open Champion in the 1990s and a four-time Major winner, carded two birdies offset by four bogies.
Charl Schwartzel fired an opening 73 to sit tied 79th, while Garth Mulroy and Thomas Aiken managed opening rounds of 74 for 98th place.
Tjaart van der Walt, Retief Goosen and Louis Oosthuizen all battled their way to 77 and were way back in 135th position. - ANA
Original source: Grace flies SA flag at US Open