The news follows the Aegis group's announcement to buy Mitchell Communications for US$300 million, reported in July.
Stephens will reportedly join a Melbourne and Sydney based digital agency following the expiration of his non-compete clause in February next year.
Steve McNaught, currently chief financial officer, will step up as chief operating officer in Australia and New Zealand. Development of the management structure is pending the shareholders vote on the acquisition of Mitchell.
"If the shareholders approve our offer to acquire the Mitchell Communications Group, the full management structure of the combined group will evolve in due course under Harold Mitchell as executive chairman,” said Nick Waters, CEO of Aegis Media Asia-Pacific.
Speaking of his departure from the group, Stephens, who was also named regional digital director in 2009, said, "The acquisition of Mitchells will ensure a bright future for the management and staff of Aegis Media Pacific, however it also represents an opportunity for me to move on."