CBS Sports' Matt Moore first reported Sept. 26 the two sides were "very close" to hammering out a deal before the Oct. 16 deadline.
It's money well earned for Harris, who has steadily developed into a key component of the Nuggets' backcourt over the past two seasons.
Following a forgettable rookie year, the Michigan State product made a leap during the 2015-16 campaign and averaged 12.3 points on 46.9 percent shooting from the field and 35.4 percent shooting from three.
The 2016-17 season represented another positive step.
Although injuries limited the 23-year-old to 57 appearances, he poured in a career-high 14.9 points per game while shooting 50.2 percent from the floor and 42.0 percent from distance.
Thanks to those figures, Harris joined Otto Porter Jr. as the only players last season to average at least 10 points and register conversion rates of at least 50 percent from the field and 40 percent from beyond the arc.
"Gary deserves so much credit," Nuggets president of basketball operations Tim Connelly said in April, according to the Denver Post's Nick Kosmider. "He's a guy who has worked his way into the player he is today. He's got a very low-key personality, so you tend to miss how productive he's been this season."
Now headed into his fourth NBA season, Harris will try to propel the Nuggets back to the playoffs for the first time since the 2012-13 campaign alongside fellow rising backcourt stud Jamal Murray and frontcourt staples Nikola Jokic and Paul Millsap.