The pair are seen pointing their respective guns in opposite directions against the backdrop of a dark city.
It comes with the tagline: "Face your past. Fight your future."
Willis and Gordon-Levitt star as the same character at different ages in the upcoming sci-fi/action project from Rian Johnson.
The film follows Gordon-Levitt's hitman Joe as he receives an order to kill his future self (Willis) after he is sent back in time.
It is set to launch this year's Toronto Film Festival on September 6.
Emily Blunt, Jeff Daniels, Paul Dano, Noah Segan and Garrett Dillahunt will also star in the film.
Looper opens at cinemas on September 28.
Watch the trailer for Looper below: