US crude prices were down 1.6 percent to $64.77 a barrel, while Brent crude lost 1.9 percent to $68.36.
The energy group retreated 1.8 percent. Suncor Energy slipped 0.8 percent to C$44.27, and Canadian Natural Resources Ltd dropped 1.2 percent to C$41.99.
The financials group slipped 0.2 percent. Bank of Nova Scotia gave back 0.4 percent to C$80.41, and Canadian Imperial Bank of Commerce lost 0.4 percent to C$120.59.
The materials group, which includes precious and base metals miners and fertilizer companies, lost 1.7 percent. Barrick Gold Corp slipped 2.7 percent to C$17.23, and Goldcorp Inc fell 2.2 percent to C$17.14.
Gold futures fell 0.9 percent to $1,332.6 an ounce. Copper prices declined 0.2 percent to $7,105.5 a tonne.
At 9:52 AM EST (1452 GMT), the Toronto Stock Exchange's S&P/TSX composite index fell 127.48 points, or 0.8 percent, to 15,733.44.
All of the index's 10 main groups were in negative territory.