Atherton joins AE from Carnival UK, where he most recently served as a regional sales manager with Cunard.
Prior to his post with Cunard, he was part of P&O Cruises' trade sales team, and has previously held roles in contact centre operations and guest services.
He started his career in travel as a baggage handler at Southampton docks, which AE said gave him "a deep understanding of the cruise industry from the ground up".
Atherton, who will be based in Southampton, will be tasked with strengthening the line's relationships with agents, supporting commercial growth and driving sales performance.
He will report into AE's EMEA sales director Andrew Turner. "James’s deep knowledge of the cruise sector, his proven ability to build strong trade partnerships and his passion for the guest experience make him a great addition to our growing team," said Turner.
"His energy and experience will play an important role as we continue to deliver unforgettable expedition voyages and broaden our reach across the UK and Ireland."
Atherton added: "Joining AE Expeditions is an exciting next step for me, both personally and professionally. I’ve long admired the brand for its commitment to sustainability, wildlife, and meaningful exploration.
"It’s a privilege to join a team that shares my values and to contribute to a company that is redefining the way we experience our planet’s most extraordinary places."