The Calgary-based company made the announcement on its website and social media Tuesday, listing the flights and affected rows.
It says passengers in affected rows are considered close contacts to those infected and could be at risk of exposure.
The airline says that public health officials are recommending people who sat in those rows to self-isolate for 14 days after arrival and monitor symptoms.
WestJet says people who were on the listed flights but not in affected rows are advised to self-monitor for signs of cough, fever or respiratory issues and to call their local health authorities if symptoms arise within the next 14 days.
The company says a total of 14 flights between Feb. 28 and March 12 had passengers on board who tested positive for COVID-19.