Humphries had his best season in 2011-12 when he averaged 13.8 points and 11.0 rebounds for the Nets. He was selected with the 14th pick in the 2004 draft by the Jazz out of Minnesota.
Wizards President Ernie Grunfeld said Saturday that "Kris is a proven veteran and will be a versatile addition to our frontcourt."
Humphries was previously married to reality TV star Kim Kardashian.
On Friday, the Wizards re-signed forward Drew Gooden.
L.A. Clippers re-sign big man Glen Davis
Big Baby is staying with the Los Angeles Clippers.
The team said Saturday that it has re-signed Glen Davis, who averaged 4.2 points and 3.0 rebounds in 23 games last season, when he joined the Clippers at the end of February.
The 28-year-old free-agent forward has also played for Orlando and Boston, where he and current Clippers coach Doc Rivers won the NBA championship in 2008.