The Bobcats trailed by two at 103-102 with 1:17 left when Williams connected on a 25-footer off a Kemba Walker assist to provide the winning margin for Charlotte (7-5), which equaled last year's entire win total with victory.
The trey was Williams' only points of the game for the Bobcats, who were led by Byron Mullens' 27 points and eight rebounds.
Ramon Sessions contributed 21 points and five boards off the bench as Charlotte won for the third time in four games overall.
Martell Webster netted 21 points and Nene added 19 for the Wizards, who fell to 0-11 -- the worst start to a season in franchise history.
Celebrity Breakups and divorces of 2014 [PHOTOS]