The agency reports that chemical products and motor vehicles were the largest contributors to the industrial index decline, while mineral fuels were the major factor in the drop in the raw materials index.
The decreases were the third in three months for both indexes.
The industrial index was up 5.1 percent in July compared with the same month a year earlier, with 14 of 21 major commodity aggregations advancing and six declining.
The raw materials index was up 19.4 percent from July 2010.
StatsCan blamed the month-to-month contraction in the industrial index on lower prices for chemicals and chemical products (down 2.6 percent), as well as motor vehicles and other transportation equipment (down 1.3 percent).
Pulp-and-paper products (down 1.1 percent) also contributed to the decline from June.
The industrial decline was moderated by upward movements in primary metal products (up 1.2 percent), and petroleum and coal products (up 0.5 percent).
The agency says the monthly drop in the raw materials index was led by mineral fuels (down 2.2 percent). Vegetable products and wood (both down 2.5 percent) also declined in July.
StatsCan says grain prices, especially wheat (down 9.7 percent), were pulled down by the events driving global demand, including the end of a ban on grain exports from Russia and the arrival of much-needed rain for North American and Asian crops.
It reports the July decline was slowed by higher prices for animals and animal products (up 1.3 percent), and non-ferrous metals (up 0.9 percent).