Separate data from Statistics Canada on Friday showed the annual inflation rate rose to 1.6 percent in September, matching forecasts and the highest in five months.
Markets and economists focused on the retail sales report, which showed sales fell 0.3 percent, against forecasts for a 0.5 percent increase. Volumes declined 0.7 percent, the biggest decrease since March 2016.
Analysts said the figures were in line with anticipated slower economic growth in the second half of the year after a strong performance that put Canada at the top of the Group of Seven.
"The Canadian economy is notably cooling down after the remarkable run it had up until about the middle part of the year," said Doug Porter, chief economist at BMO Capital Markets.
"The retail sales result does fit with that pattern of somewhat more modest activity."
It also solidified bets the Bank of Canada will hold interest rates at 1.0 percent when it meets next week after two back-to-back increases. Market odds of no move rose to 81 percent from 72.8 percent before the data was released. [CA/POLL]
The Canadian dollar weakened against the greenback following the two reports. [CAD/]
The decline in sales was led by a 2.5 percent drop at food and beverage stores, as well as stores that are typically linked to home purchases and renovations.
The increase in September's inflation rate was driven by higher gasoline prices amid supply disruptions caused by Hurricane Harvey, as well as more expensive food and shelter costs.
While underlying measures of inflation firmed somewhat, economists said they were still far enough away from the central bank's 2 percent target to allow policymakers to take their time raising rates from here.
CPI trim, which excludes upside and downside outliers, rose to 1.5 percent.
CPI median, which shows the median inflation rate across CPI components, held at 1.8 percent after the previous month was revised higher, while CPI common, which the central bank says is the best gauge of the economy's underperformance, was unchanged at 1.5 percent.
Still, many are betting the central bank will have room to hike again in December, with market odds at 47.2 percent.
(Additional reporting by Susan Taylor in Toronto; Editing by Phil Berlowitz)
By Leah Schnurr