Jethro, 11, died on the weekend from heart disease.
“We are all heartbroken by this unexpected news,” zoo manager Jeff Mitchell said Tuesday.
“Jethro was a beloved member of the zoo and an amazing ambassador to Saskatoon and the visitors at the Saskatoon Forestry Farm Park & Zoo.”
Officials said Jethro was found unresponsive on Sunday morning.
A necropsy, an animal autopsy, was carried out at the Western College of Veterinary Medicine at the University of Saskatchewan.
Veterinarians determined Jethro had hypertrophic cardiac disease, a thickening of the heart muscles that is hereditary.
Zoo officials said the disease usually shows no signs or symptoms but can lead to sudden cardiac arrest.
It will take several weeks to get the full testing and necropsy reports back.
The life expectancy of cougars is nine to 13 years.
Cougars are found from the northern Yukon down to the Andes Mountains in South America.
Cougars are classified as least concern on the endangered species list, but are considered endangered in several provinces in Canada. In Saskatchewan, cougars are a protected species.