The Teranet-National Bank Composite House Price Index, which measures changes for repeat sales of single-family homes, showed prices fell 0.3 percent last month from November.
Prices fell in seven of the 11 markets surveyed, Teranet said. Edmonton prices fell 1.4 percent, while prices in Vancouver were down 1.2 percent. It was the fifth straight month without an index rise for the most populous metropolitan area in British Columbia.
"The recent trend of home prices is clearly downward in most metropolitan markets," Teranet said in the report.
Canada's once-hot housing market has softened this year, weighed by tighter mortgage rules and five interest rate hikes from the Bank of Canada since July 2017.
Prices rose 2.5 percent in December on an annual basis, the smallest 12-month advance since 2009, Teranet said.
(Reporting by Fergal Smith; Editing by James Dalgleish)
