Economists had expected a gain of 1%, according to Thomson Reuters.
Sales rose in 11 of 21 industries, representing about 61 per cent of the manufacturing sector.
The agency says the gain was largely due to higher sales in the petroleum and coal product and motor vehicle industries.
Sales of petroleum and coal products rose 7.2% to $7.4 billion in May, while motor vehicle industry sales increased 9.3 per cent to $4.9 billion.
Sales declined 2% in the food industry, offsetting some of the overall gains in May.
“All told–a postitive release, with the volunte suggesting a solid positive contribution to monthly GDP,” said Nick Exarhos, an economist at CIBC World Markets, in a release.