Dearth of a Salesman and Insomnia is Good for You had been thought permanently lost until rolls of celluloid were uncovered in a skip outside the offices of Park Lane Films.
Film buff Robert Farrow had kept the reels among 21 film cans retrieved from the skip since 1996 when he finally opened them and discovered the lost gems.
After undergoing a hi-tech scan the films are now ready to be shown and will be played at the opening gala of the Southend Film Festival in Essex on May 1.
Members of the Sellers family are expected to attend the event.
Festival organiser Paul Cotgrove set up Dimwittie Films, named after Sellers' character in the rediscovered films, with Mr Farrow and Stephen Podgorney in order to bring them to a wider audience.
They hope to be able to fund a full restoration at a later date.
Mr Cotgrove said: "Due to Peter Sellers' iconic status with film fans around the world and the fact that he is sadly no longer with us, any 'new' material is bound to produce an enormous amount of interest.
"As these films are from the time when he was looking to make the crossover from radio to screen, they represent an important and hitherto little known part of his career.
"Consequently, I've had a lot of interest from members of the Sellers family, his friends and former colleagues and some are due to attend the gala.
"He almost appears to treat them as show reels to demonstrate to film producers his considerable talents. "
After the event, the films are expected to tour festivals around the world.
Tickets for the festival are available through www.visitsouthend.co.uk.