The publication said the Cowboys are worth $5 billion, $1.2 billion more than the second most-valuable team, the New England Patriots ($3.8 billion).
The average franchise value for a team in the league is now $2.57 billion, but Forbes notes the 2 percent increase from last year is the smallest year-over-year increase since 2010. The magazine says it's because the values are now so high that there are fewer people who could create a bidding war.
There's not a direct correlation between winning and franchise value. In fact, seven of the top 10 teams (Cowboys, Giants, Redskins, San Francisco 49ers, Chicago Bears, New York Jets and Houston Texans) didn't make the playoffs last year.
The Super Bowl champion Philadelphia Eagles came in at No. 10 with a franchise value of $2.75 billion.
Cowboys owner Jerry Jones bought the team, the most valuable in all of sports, according to Forbes, on a valuation of $63 million in 1989.