Nene injured the medial collateral ligament of his left knee during Sunday's victory over Cleveland.
The Wizards, currently seeded fifth in the Eastern Conference, said a magnetic resonance imaging exam conducted Monday revealed the extent of the injury.
The 31-year-old Brazilian has averaged 14.2 points, 5.8 rebounds, 3.0 assists and 1.2 steals over 49 games this season.
Senate Democrats to pull all-nighter on climate change
Scarlett Johansson steps out with fiance after pregnancy reveal