ST OMER, June 13, 2013 (AFP) - The 38-year-old Pretoria-born Van der Walt shot a four under par 67 to lead by one shot from France's Victor Rui.
After producing five birdies the South African said: "I managed the ball really well: I have been doing that well the last few weeks but the putting hasn't been great. I holed a few putts, which was good."
Rui was breathing down his neck after a closing birdie, birdie eagle finish having like Van der Welt started his round on the back nine.
Placed third, one shot adrift of Rui, was Briton Daniel Brooks.
Leading first round scores at the St Omer Open on Thursday (GBR & IRL unless stated, par 71):
67 - Tjaart Van Der Walt (RSA)
68 - Victor Riu (FRA)
69 - Daniel Brooks
70 - Olivier Rozner (FRA), Daniel Gaunt (AUS)
71 - Adam Gee, Ake Nilsson (RSA), Thomas Fournier (FRA), Richard McEvoy, Edouard Dubois (FRA), Terry Pilkadaris (AUS), Simon Wakefield, Chris Hanson, Justin
Walters (RSA)
72 - Roope Kakko (FIN), Robert Dinwiddie, Baptiste Chapellan (FRA), Joakim
Lagergren (SWE), Paul Maddy, Scott Henry, Simon Dyson, Oscar Floren (SWE), Carl Suneson (ESP)
73 Sihwan Kim (Nor), Mikael Lundberg (Swe), Gary Orr, David Griffiths, Luis Claverie (ESP), Alessandro Tadini (ITA), Alastair Forsyth, Francois Calmels (FRA), Jeppe Huldahl (DEN), Daniel Im (USA), Matthew Zions (AUS), Jordi Garcia Pinto (ESP), Jens Dantorp (SWE), Daniel Vancsik (ARG), Paul Dwyer, Phillip Archer, Jerome Lando Casanova (FRA), Florian Praegant (AUT), Charles-edouard Russo (FRA), Pedro Oriol (ESP), Alexandre Kaleka (FRA), Chris Lloyd