The Ontario International Airport provides domestic and limited international air travel. Because of the many manufacturing companies and warehouses in the city, the airport also serves as a major hub for freight, especially for FedEx and UPS.

Because Ontario is a major hub for passengers and freight, the city is also served by several major freeways. Interstate 10 and the Pomona (60) freeway run east-west through the city. Interstate 10 is north of the Ontario airport while the Pomona freeway is south of the airport. Interstate 15 runs in the north-south directions at the eastern side of the city. California State Route 83, also known as Euclid Avenue, also runs in the north-south direction at the western side of the city.

Ontario also has an Metrolink station off of Haven Avenue. It connects Ontario with much of the Greater Los Angeles area, Orange County and the San Fernando Valley. Public bus transportation is provided by Omnitrans.

In the years following Ontario's founding, the economy was driven by its reputation as a health resort. Shortly thereafter, citrus farmers began taking advantage of Ontario's rocky soil to plant lemon and orange groves. While few groves remain, the Sunkist Growers, Incorporated continues to operate a processing plant in the city. Agricultural opportunities also attracted vintners and olive growers. The Graber Olive House, which continues to produce olives, is a city historical landmark and one of the oldest institutions in Ontario. Dairy farming is also prevalent, as it continues to be in neighboring Chino.

A major pre-war industry was the manufacture of clothing irons. During and after World War II, Ontario experienced a housing boom common to many suburbs. The expansion of the Southern California defense industry attracted many settlers to the city.

Today, Ontario still has a manufacturing industry, the most notable of which is the Maglite corporation, which produces flashlights there. However, manufacturing has waned, and today Ontario's economy is dominated by service industries and warehousing. Much of southern Ontario still contains dairy farms and other agricultural farms. However, the area is currently under planning to be developed into a mixed-use area of residential homes, industrial and business parks, and town centers, collectively known as the New Model Colony.

In 1996, the Ontario Mills was opened on the eastern side of the city. Since then, the previously-undeveloped area has undergone a surge of commercial and residential construction.