Durham Regional Police said the shoe was found along the shore of Lake Ontario in Whitby, which is located 55 kilometres east of Toronto.
Police said a woman walking near Heydenshore Pavilion on Tuesday found the shoe and contacted police.
Further investigation led police to believe the shoe belongs to the 52-year-old father of two teenage daughters, who left for his usual early morning jog on Jan. 13 and has not been seen since.
In the days after Boucher's disappearance, police conducted an extensive ground search of wooded areas near his home. Boucher, a teacher at Bowmanville High School, is a fitness enthusiast and usually took long runs most days, often varying his running route.
In February, police used an underwater camera to check out a section of Lake Ontario in Whitby, but had to call off the search due to high winds and cold temperatures. On Feb. 2, Boucher's wife Karen told CBC News she believed her husband was dead.
Boucher is described as white, six feet tall and 180 pounds with grey and white short hair.