Statistics Canada says manufacturing sales were down 0.9 per cent in December, the first decrease since August 2013.
The agency says despite the December decline, manufacturing sales have risen in six of the last eight months and were 2.7 per cent higher than in December 2012.
Sales were down in 15 of 21 industries, representing approximately three-quarters of total manufacturing.
Transportation equipment sales fell 6.1 per cent to $8.8 billion in December after hitting a 17-month high in November.
The drop largely reflected a 19.4 per cent decline in the aerospace product and parts industry.
Sales fell in seven provinces in December, with the largest declines occurring in Alberta and Ontario.