The White Shadow was among the many silent-era movies salvaged by Hastings projectionist and collector Jack Murtagh. After his death in 1989, the highly flammable nitrate prints were sent to the Film Archive for safekeeping by his grandson Tony Osborne.
The surviving reels will be preserved at Park Road Post Production in Wellington.
Black and white duplicate negatives will be struck from the original nitrate material and colour prints made which will replicate the tints used in the original print.
"It's exciting to work on the preservation of yet another historically significant film here at Park Road and we feel privileged to be involved in such an important project," said laboratory head Brian Scadden.
The Hitchcock film is just one of the treasures uncovered, including John Ford's Upstream, the archive said. They all owe their survival to Mr Murtagh's passion for early cinema.
Mr Osborne said his grandfather was an avid collector of many things, including films, stamps and coins.
"He was known, internationally, as having one of the largest collection of cigarette cards and people would travel from all over the world to view his collection.
"Some would view him as rather eccentric. He would be quietly amused by all the attention now generated by these important film discoveries."
David Sterritt, chairman of the US-based National Society of Film Critics and author of The Films of Alfred Hitchcock, said the film's discovery was one of the most significant developments in memory for scholars, critics, and admirers of Hitchcock's extraordinary body of work.
"At just 24 years old, Alfred Hitchcock wrote the film's scenario, designed the sets, edited the footage, and served as assistant director to Graham Cutts, whose professional jealousy toward the gifted upstart made the job all the more challenging."
The first three reels of The White Shadow - more than half the film - offered "a priceless opportunity to study his visual and narrative ideas when they were first taking shape", he said.
The archive said that many other titles had been identified amongst the latest find.
The "lost" films would be preserved over the next three years in partnership with the US National Film Preservation Foundation, the Academy of Motion Picture Arts and Sciences, George Eastman House, the Library of Congress, the Museum of Modern Art and UCLA Film & Television Archive and made available in the United States.
Copies of the films would also be publicly available in New Zealand.
- NZPA