The 25-year-old full back joins the Reds after spending most of his career in his native Switzerland.
“We believe Jonas will be an important part of our club,” TFC president and general manager Kevin Payne said in a club release. “While he's still young he has solid European experience and we're pleased to welcome him to Toronto.”
Elmer was most recently with FC Winterthur of the Swiss Challenge League, where he made 21 appearances and scored once. Prior to that, he spent two seasons with FC Sion of the Swiss Super League. The full back has also spent time at FC Aarau.
Before starting his professional career, Elmer trained at the youth academies of Grasshopper and Premier League side Chelsea. Internationally, he has represented Switzerland at the youth level.
It is expected that Elmer will challenge left back Ashtone Morgan for a spot in TFC's starting XI.
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