Charlie, a chimp at the Bloemfontein Zoo, has been picking up cigarettes thrown to him by visitors and smoking them.
Zoo officials said he probably picked up the habit by observing humans.
"Baby chimps pick up habits by mimicking adults and we think he started mimicking smokers at his enclosure which probably led to smokers throwing him cigarettes," said spokesman Daryl Barnes.
Mr Barnes said Charlie was already showing the signs of a true nicotine addict: "He even acts like a naughty schoolboy by hiding the cigarette when staff approach the area."
Mr Barnes said that the zoo was determined to help him quit.