Spacey is inviting wannabe filmmakers to submit seven-page scripts to be considered for the second annual First Shot contest, organised by bosses at Jameson Irish Whiskey.
The three best candidates will get the chance to step behind the camera and work on a short film with Spacey in his role as Creative Director, while Dafoe has volunteered to be their leading man.
The Usual Suspects star has urged contestants to get creative in order to top previous entries.
Spacey says, ""In the first year of the competition we found three outstanding filmmakers and as a result we made three incredible films. Everyone's expectations are extremely high for the second year so the entrants for 2013 have a lot to live up to and, if it's possible, they have even more pressure on them to write a great story and direct an amazing film.
""We know the prize we're offering is a once-in-a-lifetime opportunity; now we need to find the talent who are worthy winners. Willem is going to be a fantastic addition to the First Shot team and I can't wait to see what people write for him - I hope entrants come up with something completely unexpected.""