The Cowboys are atop the magazine's rankings by a healthy margin for an eighth consecutive season, having risen in value by $900 million to become the only NFL team worth more than $3 billion.
Despite last having won a championship in 1996, the Cowboys are second in value only to Real Madrid ($3.4 billion) among all global sports franchises.
The Cowboys also have the NFL's highest revenue ($560 million) and operating income ($246 million), and this season become the first NFL team to have partnerships with a worldwide luxury watch and cruise line.
The New England Patriots ($2.6 billion), the Washington Redskins ($2.4 billion), the New York Giants ($2.1 billion) and the Houston Texans ($1.85 billion) round out the top five. The entire NFC East is ranked among the seven most valuable teams, with the Philadelphia Eagles coming in seventh ($1.75 billion).
Forbes says the average NFL franchise is now worth an all-time high of $1.43 billion, which is 23 percent more than a year ago and is the biggest year-over-year increase since 1999.
It is more than the mean valuation of the world's top 20 soccer teams ($1.05 billion), MLB teams ($811 million) and NBA teams ($634 million).
Only seven teams are worth less than $1 billion: the San Diego Chargers ($995 million), Cincinnati Bengals ($990 million), Oakland Raiders ($970 million), Jacksonville Jaguars ($965 million), Detroit Lions ($960 million), Buffalo Bills ($935 million) and the St. Louis Rams ($930 million).
The value of the Super Bowl champion Seattle Seahawks rose to $1.33 billion, which ranked 15th.
Other teams in the top 10 include the New York Jets (No. 6, $1.8 billion), Chicago Bears (No. 8, $1.7 billion), San Francisco 49ers (No. 9, $1.6 billion) and the Baltimore Ravens (No. 10, $1.5 billion).