Tourism Minister Trevor Holder says details will be announced Friday at the hotel which overlooks the Bay of Fundy.
New Castle Hotels and Southwest Properties have been in negotiations to buy the Crown-owned property and operate it as a Marriott.
The province launched the search for a new operator in February 2011 after Fairmont Raffles Hotels International announced it would not renew its management agreement.
The government said the century-old resort needed repairs and upgrades worth $20-million.
Holder says the agreement will ensure the Algonquin becomes a world-class facility.