Marriott shares were up 1.2% at $73.59 in afternoon trading in NY, while Starwood shares fell 3.8% to $72.18.
The combined Marriott and Starwood company would have more than 5,500 owned or franchised hotels with 1.1 million rooms globally, and would have posted more than $2.7 billion in fee revenue for the 12 months ended September.
Marriott said it expects the deal to close in the middle of next year, with the transaction contributing to earnings in the second year after the merger concludes.
The deal, executives of both chains said, offers both companies opportunities to grow, reduce costs and attract younger travelers.