Ex-Dentsu Americas Boss Sean Reardon Returns to Publicis as Epsilon CEO

After stepping down as Dentsu Americas leader in May, Sean Reardon is returning to Publicis Groupe as chief executive (CEO) of Epsilon.

It marks the first time the holding company’s data business, part of its connected media unit, has had a CEO since Bryan Kennedy retired in 2021.

John Giuliani, who had been serving as Epsilon’s executive chairman, will remain in his role. Per a company release, he will work with Reardon to drive Epsilon’s growth, while also focusing on long-term strategic initiatives.

Reardon and Giuliani will report to Dave Penski, CEO of Publicis Connected Media. Reardon will also join the Publicis Groupe management committee.

“Sean’s rich understanding of the complexities of this business, alongside the opportunity found in bringing together data, digital, commerce, and influencer capabilities within our Connected Media offering, will only continue to drive growth, differentiation, and powerful outcomes for our clients,” Penski said.

A Publicis vet

Reardon is based in Atlanta, Ga., where Coca-Cola, one of Publicis Groupe’s newest media clients, is also headquartered. The business snagged Coke’s $700 million North America data and media business from WPP in March. Another recent win includes LinkedIn’s media business, previously held by Dentsu.

Reardon’s new position marks his return to the French advertising giant. He previously served in various senior roles, including CEO positions, at its now consolidated digital media agencies, Zenith and Moxie, between 2007 and 2019.

The exec joined adtech firm MiQ as U.S. CEO in 2019, adding global to his title in 2022. The seasoned leader took on his most recent role at Dentsu in 2024.

He arrives as Publicis has been bulking up its data arsenal. It recently acquired ID business Lotame, which it is integrating into data powerhouse Epsilon to help clients reach 91% of adult internet users globally and deliver “personalized messaging at scale.”

ADWEEK understands Reardon will oversee Lotame as part of his remit, following its integration with Epsilon.

In October, Publicis CEO Arthur Sadoun told ADWEEK that media accounts for 60% of Publicis’ net revenues.

The holdco has made several big appointments since the end of last year. In December 2024, it tapped Amy Armstrong from Amazon Ads as its chief revenue officer. In March, it named former BMB creative Matt Lever as its global executive creative director.

It also recently promoted Deepti Velury to CEO of global production to lead production, as well as AI and data integration within its connected media arm.

The company ended 2024 as the largest advertising and marketing services company among the “big four” ad networks by revenue. However, that designation won’t last long following Omnicom’s impending takeover of IPG.

Changes at Dentsu

Will Swayne, global practice president of media at Dentsu, filled Reardon’s role in May with an expansion of his purview into the U.S.

“Media is the driver of Dentsu’s integrated growth solutions powered by creativity, data, and technology, and through this shift, we aim to achieve consumer connectivity for our clients’ brands at scale,” a Dentsu spokesperson said in a statement at the time of Reardon’s departure.

“The U.S. is emerging as a key driver of media opportunity and leadership and will continue to be an area in which Dentsu invests in talent and capabilities.”

Having laid off 8% of staff in August, Dentsu is reportedly mulling a sale of its international business, according to The Financial Times.