The disclosure ended weeks of speculation about what killed the Grammy-winning singer on February 11 on the eve of the awards.
Houston was found submerged in the bathtub of her room at the Beverly Hilton Hotel, and her death was ruled accidental.
“The final cause of death has been established as drowning due to atherosclerotic heart disease and cocaine use,” Craig Harvey from the LA County Coroner's Office said on Thursday.
Several bottles of prescription medications were found in her hotel room, but coroner's officials said they were “not considered to be related to the actual cause of death.”
The singer also had a heart disease that caused blockages in her arteries.
“The cocaine use indicated an acute use, and it appeared that the cocaine had been used in the time period just, probably, immediately prior to her collapse in the bathtub at the hotel,” he added.
“We are saddened to learn of the toxicology results, although we are glad to now have closure,” Patricia Houston, the singer's sister-in-law and manager, wrote in a statement to The Associated Press.
The exact amount of cocaine in Houston's system was not disclosed on Thursday but will be contained in a full autopsy report to be released in about two weeks, officials said.
Toxicology results also showed Houston had marijuana, Xanax, the muscle relaxant Flexeril, and the allergy medication Benadryl in her system.
Beverly Hills police said in a statement there was no evidence of wrongdoing in connection with Houston's death. Houston died just hours before she was scheduled to appear at producer Clive Davis' pre-Grammy Awards bash.
A sensation from her first, eponymous album in 1985, Houston was one of the world's best-selling artists from the mid-1980s to the late 1990s, turning out such hits as “I Wanna Dance With Somebody,” “How Will I Know,” and “I Will Always Love You.”
Houston, 48, was buried in a New Jersey cemetery next to her father.