Economists had expected a gain of 1.0 per cent, 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 per cent to $7.4 billion in May, while motor vehicle industry sales increased 9.3 per cent to $4.9 billion.
Sales declined 2.0 per cent in the food industry, offsetting some of the overall gains in May.
Manufacturing sales rose in six provinces in May, with almost two-thirds of the gain concentrated in Ontario.