The two companies have begun integrating their U.S. operations, Uber said.
Shares of Uber, San Francisco, at last check were up 2.7% to $51.02.
The companies will "continue to innovate, bringing ever-better products and services for merchants, delivery people, and consumers across the country,” Uber Chief Executive Dara Khosrowshahi said in a statement.
Uber said Postmates would contribute $350 million to $400 million to gross bookings for delivery and increase adjusted earnings before interest, taxes, depreciation and amortization by $7 million to $12 million for the quarter ended Dec. 31.
“I'm confident that alongside Uber Eats we will create even more opportunities for our customers, continue to drive growth for our merchants, and deliver unique earning opportunities" for its delivery workers, Postmates Co-Founder and CEO Bastian Lehmann said.
Uber said it will also start a regional listening exercise for merchants across the country, next year, as the company starts to bring together Uber Eats and Postmates.
"The goal is to bring our leadership closer to the incredibly diverse spectrum of merchants using the Uber Eats and Postmates platforms," Stephane Ficaja, head of Uber Eats U.S. and Canada, said in a company blog post.
The combined company aims to "better listen, understand, and build for the challenges and opportunities our partners face," he wrote.
In July, Uber agreed to acquire Postmates for $2.65 billion in an all-stock deal.
The deal fits into Uber's diversification strategy, with ride-share traffic falling amid the coronavirus pandemic, while consumers stuck at home due to lockdowns have ramped up ordering from restaurants offering takeout.