Fines have kicked in for Montreal merchants who give customers thin plastic bags.
The ban was implemented on Jan. 1 but retailers were given a five-month grace period.
The measure covers the distribution of lightweight plastic bags with a thickness of less than 50 microns as well as biodegradable bags, which contain an additive that causes them to decompose in heat and light.
There is an exception for the thin bags that are used in grocery stores to transport fruit and vegetables to the cash register or to wrap up meat.
City officials have said lost or abandoned plastic bags are a visual nuisance that cause considerable harm to terrestrial and marine ecosystems and often end up in landfills.
The ban is intended to encourage people to move away from single-use products and to adopt reuseable bags.
Thicker plastic bags, paper bags and cardboard boxes will also be allowed.
Individual retailers could face fines of up to $1,000 for a first offence and $2,000 for subsequent offences.
For corporations, the fine can be as high as $2,000 for a first offence and $4,000 for subsequent offences.
Victoria has also announced its intention to ban plastic bags this July.
Several smaller Canadian municipalities have imposed their own bans, while Toronto tried and failed to do so in 2012.
Retail and plastic industry advocates have opposed the bans, arguing they are unnecessary as well as troublesome for businesses and consumers.