Millsap's agent, DeAngelo Simmons, confirmed the agreement to ESPN and The Athletic on Thursday. According to the outlets, the veteran forward considered multiple playoff contenders -- including the Golden State Warriors, Los Angeles Clippers and Chicago Bulls -- before agreeing to join the Nets.
Brooklyn has yet to confirm the agreement.
The 36-year-old Millsap becomes the latest former All-Star player to reach a deal with the Nets, joining Kevin Durant, Kyrie Irving, James Harden and Blake Griffin. Millsap's four All-Star appearances bring the Nets' team total up to 38.
Millsap averaged just nine points and 4.7 rebounds over 56 games for the Nuggets last season. He then averaged only 6.4 points and 3.9 rebounds in 12.1 minutes per game during Denver's two playoff series this past postseason.
Millsap will help stabilize the Nets' frontcourt rotation after the team lost veteran Jeff Green, who signed with the Nuggets earlier this off-season.
The Utah Jazz selected Millsap in the second round of the 2006 NBA Draft out of Louisiana Tech. In 1,052 career games (745 starts) with the Atlanta Hawks, Jazz and Nuggets, he has averaged 13.7 points and 7.2 rebounds.