Susanna Frayn has been promoted to comms director and will report to director of people John Athanasiou.
Sam Missingham joins from The Bookseller in the newly created role of head of events and James Lewis has been promoted to comms content officer.
Team assistant Sarah Patterson has decided to return to Australia and will leave the company on 6 December.
Frayn joined the publisher in 2001 as comms director, coming from the BBC, where she headed up the factual publicity team. She has worked part-time as comms manager since returning to work after maternity leave.
Missingham was head of events and marketing at The Bookseller for five years.
Lewis has been with HarperCollins for two years, since graduating from the University of Nottingham.
Frayn told PRWeek that for the moment there would be no change of comms strategy. "We’re getting the right people in place and then looking to take things forward," she said.