As a clerk, Andrew joined the newly organised shipping firm of Edmonstone, Allan & Co., of which his brother, Hugh, was partner.

By 1857, the Allan family were the sole owners, whose chief advantage over their competition was the use of iron-hulled steamships with screw propellers.

There was never any doubt that Hugh Allan was the driving force behind what became Canada's leading steamship company, and the multitude of his other business interests.

"[1] When Hugh died in 1882, Andrew took his place as head of the Allan family's Canadian enterprises, presiding over the peak of the shipping firm's worldwide cargo and passenger activities in the 1880s and 1890s.

Andrew had kept things as they were under his brother, but by 1897 it was necessary to make some major changes, in part to raise additional capital for a new fleet of ships.

Since its creation, the bank had been used by the Allan family, including Andrew, to finance their personal investments, particularly in Manitoba and towards the North Western Railway.

Andrew had enjoyed relative success in shipping and banking, but his involvement with the Manitoba and North Western Railway Company of Canada was a failure.

Despite expansive and enthusiastic lobbying, by 1894 the Allans could not afford the interest payments on its debt and the company was put into receivership.

The fact that Andrew took little direct part in the negotiations perhaps indicated the rise of younger family members within the Allan hierarchy.

While he lacked his brother's entrepreneurial flair and despite his failure with the railway in the Canadian West, he nonetheless steered the Allan Line through the height of its success, and when needed, stepped up to re-organize the family firm ready for his many sons and nephews on both sides of the Atlantic Ocean to take them into the 20th century.

The Allans home, Iononteh, was a greystone mansion that dominated Upper Peel Street in the Golden Square Mile, near to Andrew's brother's house, Ravenscrag.