It is one of ten regional sites being sold by the group as part of a plan dubbed Project Solstice.
The Imperial served as a hospital for shell-shocked officers in the First World War and as the Ministry of Agriculture, Fisheries and Food in World War II.
Now a four-star hotel, it features 180 rooms, a restaurant, bar, health club and 600-capacity conference facilities.
Martin Rogers, head of UK hotel transactions at Savills, which is representing The Hotel Collection alongside Rothschild, said: “The Imperial Hotel is a true reminder of Blackpool’s Victorian heyday, combining 19th century opulence and glamour with contemporary style and modern facilities.
“The successful restaurant, health club and conference facilities means it offers prospective new owners several income streams.”
The Imperial Hotel in Torquay was announced as the first sale in Project Solstice in August after it was bought by the Brownsword Hotel Group.
Other Hotel Collection properties up for sale include The Old Ship Hotel in Brighton and The Billesley Manor Hotel in Stratford-upon-Avon.
The company, previously known as Puma Hotels, was rebranded as The Hotel Collection in 2014 by owner Lone Star.