Average apartment prices were 19 times the gross annual median income, the US-based Demographia found, up from 17 times in 2014.
Hong Kong's housing market was also ranked the most expensive in the world for the sixth straight year in the survey, which considered prices in the third quarter of 2015 in 367 cities.
Observers pointed out that the Hong Kong real estate market could drop.
"The investment mood is deteriorating," Simon Lo, executive directorat Colliers International, was quoted as saying by the South China Morning Post. He said home prices would likely drop 15 per cent by the end of 2016.
Hong Kong was followed by Sydney, with a rating of 12.2, and then Vancouver, at 10.8, according to Demographia, which considers anything above 5.1 to be "severely unaffordable."
A 40-square-metre apartment in Kowloon costs on average 4.34 million Hong Kong dollars (560,000 US dollars), or around 14,000 dollars per square metre, the SCMP report said, citing the authorities' Rating and Valuation department.
- DPA