Due to time already served, that means that Cilic is free to compete at next week's Paris Masters.
Former world number nine Cilic appealed the ban imposed on him after he tested positive for the banned stimulant nikethamide.
Cilic insisted he had never knowingly or deliberately taken any banned substance and unbeknownst to him the stimulant was in glucose tablets he had taken.
The Court of Arbitration for Sport ruled that the International Tennis Federation ban was "too severe in view of the degree of fault."
Cilic tested positive for nikethamide at the BMW Open in Munich in April this year. Nikethamide is banned in competition although it is allowed out of competition.
Cilic has not played since withdrawing from his second-round match at Wimbledon in June but retains a ranking of 47th in the world.
The tall right-hander reached a career-high ranking of ninth in the world in February 2010, spending 11 successive weeks in the top 10.
His ban officially ends at midnight on Friday.