Honda spokesman Ron Lietzke said the upgrades will continue the company's effort to localize the manufacturing of its products in North America.
Honda will spend about $170 million to add a fourth engine assembly line and make other upgrades at the plant in Anna, adding about 200 new jobs. Construction will begin in the next few months at the plant about 50 miles north of Dayton.
Another $50 million investment at the transmission plant at Russells Point, about 60 miles northeast of Dayton, is in addition to a round of previously announced new spending at the facility. The projects will "increase flexibility to produce advanced transmissions and powertrain components," the company said.
The Russells Point upgrade will result in some new jobs, but the company said it will announce details later.
Honda said it has invested about $475 million at those plants within the past two years.
The Anna facility is Honda's largest engine plant. It employs about 2,600 people and produces four-cylinder and V6 engines and drivetrain components. The roughly 1,100 employees at the Russells Point facility make automatic transmissions and four-wheel-drive systems.
Honda's new Accord sedan being built at the company's Marysville plant in central Ohio has led to investments and more jobs in the Anna and Russells Point plants, with companies that supply Honda with products and services also getting a boost.
Overall, Honda has about 13,500 Ohio employees in manufacturing, support, research and development and other operations.
Honda has nine automobile assembly lines at seven plant sites in North America, with an annual capacity of 1.63 million Honda and Acura cars.