Prior to his switch to academia in 2008, Sheehan spent 25 years with Saatchi & Saatchi Advertising. After five years in S&S’s New York headquarters, he spent the next 11 years overseas, working in S&S Hong Kong, and as CEO of S&S Japan and S&S Australia. He then spent nine years as chairman and CEO of Team One Advertising in Los Angeles (a division of Saatchi & Saatchi).

In his career, Sheehan has worked with many top national and international brands, including Toyota, General Mills, Procter & Gamble, Hilton, British Airways, IKEA, TIME, News Corporation, Bayer, DuPont, Sara Lee, Kodak, Ritz-Carlton, Castrol and Hewlett-Packard.

Sheehan has consulted for a number of national and international companies, including Petrobras, Brazil’s national energy company and Intesa Sanpaolo, Italy’s largest bank. He has also been an advisory board member of a number of digital companies.

In 2010, Sheehan published his first book, “.” In 2011, he published his second book, “.” In June 2013, he published his third book, “.” In 2020, he published “,” an advertising textbook he co-authored with fellow Newhouse advertising professor Ed Russell.  The book is being used in over 30 universities.

Sheehan publishes regularly in Advertising Age and Adweek, and has published articles in peer-reviewed advertising journals, including the Journal of Advertising Research.