It has also approved Russia's Sputnik V vaccine for usage in India.
The vaccine was authorised in December for use in Canadians 16 and older.
The country had started the COVID-19 vaccination drive on January 16 with two vaccines - Covishield (Oxford-AstraZeneca's vaccine manufactured by Serum Institute of India) and Covaxin (manufactured by Bharat Biotech Limited).
The U.S. Centers for Disease Control (CDC) Director Rochelle Walensky said earlier in April that the vaccine could be approved by mid-May.
The two-shot vaccine was Pfizer's top-selling product in the first quarter.
More than half of Americans have received at least one dose of a vaccine.
"After completing a thorough and independent scientific review of the evidence, the department determined that this vaccine is safe and effective when used in this younger age group", Health Canada's chief medical adviser Dr. Supriya Sharma said on Wednesday.
Trials are underway by Pfizer and other drugmakers for other age groups, including children as young as six months.
Sharma said the pharmaceutical giant has indicated it could be submitting its submission to expand use to children ages five to 11 as soon as September.
Expenses and profit from the vaccine are split 50-50 between Pfizer and its German partner BioNTech.
Kids studied had side effects similar to young adults, the company said, mainly pain, fever, chills and fatigue, particularly after the second dose.
Since the beginning of the pandemic, about 20 per cent of COVID-19 cases have been reported in people under the age of 19, she adds.
The drugmaker is expected to provide additional information of the vaccine's safety, efficacy, and quality to Health Canada as part of conditions in the agency's interim order.
The vaccine is an mRNA vaccine, which means it teaches cells how to make a protein that triggers an immune response, without using the live virus that causes COVID-19. A total of 4.12 million doses of vaccines had been shipped in as of Monday.
Asked what this might mean for schools to be able to reopen, Sharma said that'll depend on how and when provinces and territories decide to administer these shots to younger people.