Mannion spent most of his professional career with the Philadelphia Phillies, serving in a variety of positions from 1982-1997, most recently as vice president of marketing.
The move continues the club's post-season reorganization, which included the resignation of Manager Grady Little and the hiring of Joe Torre Monday as his successor.
"We are delighted to bring Dennis to the Dodgers during these exciting times," said Dodgers Vice Chairman and President Jamie McCourt. "He allows us to accelerate our business operation because of his vast and diverse sports background and reputation for innovation."
Mannion comes to the Dodgers after eight years as senior vice president of business ventures for the NFL's Baltimore Ravens. He was also was senior vice president of Ascent Sports, owner of the NBA's Denver Nuggets and the Colorado Avalanche of the NHL.