The group, which is based in Leamington Spa, and has been manufacturing its stoves in Coalbrookdale, Shropshire, since 1930, said it had agreed a sale with the Middleby Corporation.
The US firm said it would carry out a strategic review of operations later in the year, once the deal is completed.
It said it planned to keep Aga's manufacturing in the UK.
Last year, Aga announced a fall in profits, mainly because of pension costs, shop closures and site rationalisation, although revenues rose.
However, it said markets for its appliances had strengthened at the start of the year.
The group, which also owns the Fired Earth tiles brand, recently began sales in China after spending more than two years gaining the right accreditations.
Selim Bassoul, chairman and chief executive of Illinois-based Middleby, said the takeover would strengthen the company's global reach.
Aga said the deal would help increase sales of its brands in North America, while the British firm would offer Middleby a "European platform".
The first Aga oven was designed by Swedish Nobel Prize-winning physicist Gustaf Dalen in 1922 and production started in the West Midlands seven years later.
The cast-iron cooker maker Aga Rangemaster is to be sold to a US firm in a deal valued at £129m.