"Happy 70th Birthday, Mandy!" Elwes wrote in the caption. "It seems like just yesterday when we took this photo at the premiere!"
The film, which has captivated audiences since it premiered 35 years ago, stars Elwes and Patinkin, who play Westley and Inigo Montoya, respectively.
In 2011, the cast -- which included actress Robin Wright, Billy Crystal and Wallace Shawn -- reunited on "Good Morning America," where they talked about the impact of the film, its memorable quotes and what they remember most from the movie.