The Edinburgh stand-off became Scotland qualified in the middle of last month and was fast-tracked into the starting line-up for the match with Ireland in Dublin.
Although the Scots lost 31-16 at the Aviva, Townsend felt van der Walt acquitted himself impressively.
“I thought he did really well,” said the Scotland coach. “He looked comfortable at international level. There were a couple of errors, probably from the excitement of being his first time playing at this level. But I felt he was physical in defence.
“We looked to move the ball wider in the second half and there were a few times we did get width and it eventually opened up space for Duhan van der Merwe’s try.”
Van der Walt is eligible for Scotland through the three-year residency rule and is the third South African to be blooded by Towsend during this international window. He is also the fifth player to play at stand-off for the Scots during the autumn series after Adam Hastings, Finn Russell - both injured against Wales - Stuart Hogg and Duncan Weir.
Van der Walt travelled to South Africa to get married last month and had to isolate on his return, meaning his training time with the squad was minimal.
“He should be really pleased with the way he performed and that’s on the back of two training sessions,” said Townsend. “So to come in for your first cap on the back of quarantine, meeting your new team-mates, training with them for the first time and then producing a performance like that - that’s a big positive.”
The fly-half assumed place-kicking duties against Ireland and his first penalty attempt was a monster effort from over 50 yards which was still rising as it struck the upright.
“Yeah, I was actually confident,” said the player. “I was looking down and when I looked up it hit the sticks so it wasn’t ideal but obviously in this type of game you look ahead to what’s up next, you can’t dwell on a missed kick and for me the best way is to forget about it and move on.”
He did just that, kicking the next three penalties as Scotland established a 9-3 lead before being clawed back in the fatal ten minutes before half-time. Van der Walt also converted van der Merwe’s try to give himself an 11-point haul on his debut and a respectable 80 per cent success rate off the tee.
Scotland’s next assignment is the 2021 Six Nations and while Russell is expected to be fit, doubts remain about Hastings’ availability, opening the door for van der Walt to be involved when they open their campaign against England at Twickenham in February.
“Finn is one of the best 10s in the world so it’s just about learning from them and training with them, and we can feed off each other,” said van der Walt of his fly-half rivals. “I’m happy whenever they want to play me, if I get the opportunity I just need to play well again but for me it’s just a learning curve.”