The 26-year-old, who joined the club in 2009, is on the verge of becoming the Warriors' all-time leading tryscorer.
"This was a pretty easy decision for me and I'm very happy to have signed the deal," said Van der Merwe.
"The direction the squad is heading played a big factor in my decision to stay in Glasgow, not just the guys who are playing here already but the guys who want to come and play their rugby here too. It's pretty exciting.
"I've been lucky enough to play in a couple of semi-finals with this club and it would be great to take it that one step further on. This squad definitely has the potential to win some silverware."
South Africa-born Van der Merwe has represented Canada 24 times at senior international level, scoring 65 points.