Cousins will miss Thursday night's game at Miami.
The NBA announced the penalty a day after Cousins and Horford tangled late in the first quarter at Atlanta. The 25-year-old Cousins has often been suspended for his conduct on and off the court.
The 6-foot-11 Cousins has averaged 27.5 points and 11 rebounds this season in eight games for the Kings. He has missed four games because of a strained right Achilles.
Cousins made the All-Star team last season.