The deal reunites the Patriots' first-round choice in 2006 with Josh McDaniels, New England's offensive coordinator before he became Denver's head coach last season. The trade is pending a physical examination.
The Patriots gave up on Maroney after he failed to emerge as a solid No. 1 back since being drafted out of Minnesota. He was limited by a shoulder injury to three games in 2008. In four years with New England, he rushed for 2,430 yards and 21 touchdowns and tended to run side to side rather than hit openings quickly.
Maroney led New England's rushers with 757 yards and nine touchdowns last season and ran for a career-high 835 yards in 2007.
Their backfield has been in a state of flux ever since starter Knowshon Moreno (hamstring) and backup Correll Buckhalter (back) were injured during the first 7-on-7 drill of training camp on Aug. 1.
Denver brought in free agent LenDale White, but he sprained his ankle on his first full day of workouts and then tore his right Achilles' tendon in the preseason finale. He is out for the season after undergoing surgery last week.
The Broncos rushed for 89 yards and one touchdown on 25 carries in their 24-17 loss to Jacksonville in Sunday's opener. Moreno, who missed all of the preseason, gained 60 yards on 15 carries with one touchdown, and Buckhalter, who had just a handful of carries before the opener, ran six times for 15 yards.
Lance Ball, a second-year pro who was cut four times before being signed to the Broncos' practice squad last November, capitalized on his carries during camp to earn a roster spot, and the Broncos brought in Andre Brown, who was cut by the New York Giants. He missed the opener with a turf toe injury.
Moreno was McDaniels' first draft pick after coming to Denver to replace Mike Shanahan. But the 12th overall pick in the 2009 draft out of Georgia hurt his knee on his first series in that preseason after a protracted holdout that had fans nicknaming him "Know-show." He never seemed to find a rhythm during the regular season, failing to record any 100-yard games and repeatedly failing in short-yardage situations.
The Associated Press contributed to this report