Joel Cohen and Ethan Cohen's upcoming movie is loosely based on the life of 1960s Greenwich Village folk musician Dave van Ronk.
Serralles, who is best known as a stage actress and previously appeared in James Gray's Two Lovers and Julie Taymor's Across the Universe, is the latest addition to the cast, according to Variety.
She also recently made a guest appearance on CBS drama The Good Wife.
Serralles will join Oscar Isaac, Carey Mulligan, Justin Timberlake and John Goodman in the movie, which is based on Ronk's memoir The Mayor of MacDougal Street.
Isaac (Drive, Sucker Punch) will take the lead role, with Timberlake co-starring as a fellow folk musician who is married to Mulligan's character.
Serralles's role in Inside Llewyn Davis is currently unknown.
The movie is being produced by Scott Rudin and co-financed by StudioCanal, with production due to begin early next year.