Dallas is worth $5 billion, up from $4.8 billion from a year ago. The Cowboys also led with a profit of $365 million.
The NFL dominated the rest of the top 50, with 26 of the league's 32 teams landing a spot.
The New England Patriots (seventh, $3.8 billion), New York Giants (tied for 10th, $3.3 billion), and Los Angeles Rams (12th, $3.2 billion) were the next three football teams on the list.
Forbes credited the Cowboys' success to the innovations of owner Jerry Jones.
"Jones has always been a visionary since he bought the Cowboys for $150 million 30 years ago," Forbes' Kurt Badenhausen wrote. "He revolutionized stadium sponsorships; broke away from the NFL's shared merchandise revenue system; launched a stadium-management firm, Legends Hospitality, with the New York Yankees; and opened a $1.5-billion practice facility in 2017."