The black and white picture was taken by the captain of another steam ship, the S.S. Etonian, two days before the fatal collision in 1912, Yahoo! News reported.
In a caption at the bottom, Captain W F Wood identifies the iceberg as the "blueberg" -- an iceberg made blue by the sun's rays -- that sank the Titanic in three hours.
Experts believe it's the same iceberg because it was photographed in the right area and matches descriptions and sketches from that time.
The 13x11-inch photo is one of more than 400 Titanic memorabilia items to be sold by American auction house RR Auctions next month, according to The Daily Mail.
It's expected to fetch between $8,000 and $10,000.
A handwritten caption, scrawled directly onto the developed picture states the coordinates of the iceberg as 'Latitude 410 0 W Long 490 50 N' - not far from the widely documented position where Titanic sunk.
The caption scribbled on the photo reads: ‘Blueberg taken by Captain Good S. S. Etonian on 12/4/12 in Lat 410 50 W Long 490 50 N. Titanic struck 14/4/12 and sank in three hours."
Frederick Fleet, the lookout on duty who first spotted the iceberg, and Joseph Scarrott, an able-bodied seaman, both drew sketches of the ice which are eerily similar.
A spokesman for RR Auction, which are selling a total of 408 items in connection with Titanic said, "The story of the Titanic still resonates both here in America as well as in England. To be able to auction a photo of the iceberg that sank the unsinkable is quite remarkable and something we are proud to offer to our clients from around the world."