The Cowboys, who have only made the playoffs four times in the last 12 seasons, are worth $8billion, up 23% from last year, Forbes said.
The New England Patriots ($6.4billion), Super Bowl champion Los Angeles Rams ($6.2billion), New York Giants ($6 billion) and Chicago Bears ($5.8billion) completed the top five.
According to Forbes, the average value of the NFL's 32 teams rose 28% percent from last year to $4.47billion due in part to the $4.65billion sale of the Denver Broncos to the Walton-Penner ownership group led by Walmart heir Rob Walton.
The Cincinnati Bengals ($3billion), who fell 23-20 to the Rams in last season's Super Bowl, were the NFL's lowest-valued team on the list.