Markus Dohle, the chairman and chief executive of Random House, who will take on the role of chief executive of the new company, announced the completion of the merger in an e-mail to employees on Monday.

“Today, we are Penguin Random House,” he wrote. “You should be proud of what you’ve accomplished and what we are all now a part of: the first truly global trade book publishing company. Together, we are even better positioned to fulfill our core purpose: to bridge authors and readers by publishing the very best books.”

Bertelsmann, the owner of Random House, and Pearson, the owner of Penguin, disclosed the merger in October, saying that Bertelsmann would control 53 percent of the company and Pearson 47 percent. Since then, the merger has sailed through regulatory approvals in the United States and Europe, as well as China, Canada and other countries.

The combined companies will control more than 25 percent of the book business, with more than 10,000 employees, 250 independent publishing imprints and about $3.9 billion in annual revenues.

Mr. Dohle, in a telephone interview from London, where he was about to embark on a three-week tour around the globe to meet with employees, said that part of his message is simple: there will not be much change at first.