The agency says sales were down in the miscellaneous, food and motor vehicle assembly industries, although these declines were largely offset by gains in the aerospace product and parts and primary metal industries.
Sales were down in 11 of 21 industries, representing just over 40 per cent of manufacturing sales.
Non-durable goods sales declined 0.7 per cent to $24.6 billion while durable goods sales rose 0.4 per cent to $24.9 billion.
Sales were down in five provinces in August, with the largest decline in Ontario, where sales fell 2.1 per cent to $22.5 billion.
Quebec manufacturers, however, reported a 3.2 per cent gain to $11.6 billion, a third consecutive monthly increase.