The deal is subject to approval by the Competition Bureau but is expected to close in the first quarter of 2015.
Mattamy says it will then work with Monarch over the following months to integrate the two organizations.
The addition of Ontario-based Monarch will solidify Mattamy's position as Canada's largest home builder.
Mattamy is a private company based in Oakville, Ont. It has built communities in the Toronto area, Ottawa, Calgary and Edmonton as well in several U.S. metropolitan areas in Minnesota, North Carolina, Arizona and Florida.
Arizona-based Taylor Morrison says it expects to receive $570 million cash as a result of the transaction, including $240 million currently at Monarch.
The U.S. homebuilder says the money will strengthen its ability to invest in strategic locations in the United States.