More entrances are also being added, as well as extra parking. The mall will remain open while the development is going on.
City leaders say they're trying to boost the local economy by adding more jobs and increasing sales tax revenue.
"Ontario Mills is an important asset to all that our city has to offer and we recognize its many great benefits, including valuable economic growth and more jobs for years to come," said Ontario Mayor Paul Leon. "We are committed to our residents and businesses and will continue to be a strong and economically viable city, providing the very best in quality shopping, dining and entertainment."