The South African-born Canadian winger has made a big impression during his two-years at Firhill and bagged 11 tries in 25 appearances.
He is hoping to continue his red-hot form and repay the faith Glasgow head coach Sean Lineen has shown in him.
"Having been given the opportunity two years ago, which I have to thank Sean for, it was a pretty easy decision to stay," said Van der Merwe.
"I've got used to life here, the fans and the city, and I'm comfortable now playing in the team.
"It's been a good learning curve. Every day I think I've learned something new on the field and have improved as a player and hopefully I can just continue getting better for Glasgow.
"This season is not the way I'd like things to have gone, but obviously last year proved that we could play against the best teams and hopefully in the next two years we can do that again.
"Our team doesn't have 15,000 people at every game, but the two or three thousand that do show up you can certainly hear on the field and they're behind you every step of the way.
"Even in the bad times they show up so and that's attracted me to Glasgow. It's a young team but we're learning together and hopefully we can prove that we're quality players."
Resigned to losing internationals Max Evans, Richie Vernon and Kevin Tkachuk in the summer, Lineen was delighted to retain the services of Van der Merwe who he sees as a future star.
"He has only been a professional for two years and is the second top try-scorer in the league this season and we haven't have a great season," said Lineen.
"When you look at all teams you need that X-Factor and DTH has certainly got that. Sometimes you wonder what he's doing, but he conjures up tries from nowhere and you've got to have guys like that in the team.
"If you look at teams around the world, especially the back threes have guys that can score tries and produce little bits of magic and that's what we need.
"Over the last few years you look at the likes of Lome Fa'atau and Bernardo Stortoni, who have developed here and loved it here, they were important to us and DTH is another to come along and stamp his mark on the game.
"He's tough, he's fast and knows his way to the try-line and he's fantastic to work with
"If he's got some ideas or points of view he'll let you know and that's what you want from players; you want them to challenge you.
"He's quickly developed into a senior member of the squad; a senior player. He's going to be very important to us moving forward."
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