Justin Trudeau says if elected, his Liberal government would start taking action to legalize marijuana "right away."
Trudeau reiterated the promise on Wednesday evening at a rally in Quebec City.
He says he wouldn't be comfortable seeing pot sold anywhere and would focus on strictly regulating its sale, similar to what has happened in "Colorado or elsewhere."
Trudeau says legalization would actually make it easier to keep pot out of the hands of children as well as bring in extra tax dollars.
"What is very clear right now is that Mr. Harper’s current approach is making marijuana too easy to access for our kids, and at the same time funding street crime, organized gangs and gun runners," Trudeau said.
The Liberal leader also said he would "work with the provinces to makes sure that the control and regulation of marijuana is done in a way that is responsible."
Conservative MPs have in the past accused Trudeau of planning to make marijuana available in corner stores, and therefore easier for children to get their hands on.
"My focus is on making it more difficult for young people to access it," Trudeau said.
"At this point, I don’t think corner stores necessarily are rigorous enough at checking ID to make me comfortable with that as an option."
NDP Leader Tom Mulcair has previously said he supports decriminalization of marijuana, but has not committed to legalization.
"The NDP for 40 years has believed that it makes no sense at all for a person to have a criminal record for possession or personal use of a small amount of marijuana," Mulcair said last year.
In Colorado, which legalized recreational marijuana sales as of Jan. 1, 2014, only licensed stores may sell cannabis and those stores are prohibited from selling most other products, including cigarettes, alcoholic drinks and non-alcoholic drinks.
