The Cowboys, often described as "America's Team (NYSE: TISI - news) " despite not having won the Super Bowl since 1995, topped the Forbes list with a value of $4 billion (3.5 billion euros), fueled in part by the NFL's gargantuan domestic television deal.
The valuation puts them ahead of Real Madrid, who were valued by Forbes at $3.26 billion according to a global list released earlier this year.
Two other US sports franchises, the NFL's New England Patriots and baseball's New York Yankees, were next with an estimated value of $3.2 billion.
Reigning European champions Barcelona came in at fifth with an estimated value of $3.16 billion.
Premier League giants Manchester United (NYSE: MANU - news) were valued at $3.1 billion according to most recent Forbes estimates.
Forbes said the Cowboys have surged to the top thanks to revenues of $620 million, some $100 million more than its nearest high-earners in the NFL.
The third most valuable NFL team according to Forbes are the Washington Redskins at $2.85 billion with the New York Giants next at $2.8 billion.
The San Francisco 49ers came in at $2.7 billion, up nearly 70 percent in value since their last appearance on the list.
The spike was attributed to the team's move to their new state-of-the-art stadium at Santa Clara.