Reese Witherspoon was starstruck working with acting legend Jack Nicholson on her new comedy How Do You Know.

“Oh my gosh, it blows your mind when you walk on set and there he is,” the actress admitted on the red carpet at the film’s LA premiere.

“He’s standing there and he’s laughing, smoking a cigarette, and you’re like ‘Oh my god this is not really happening’,” she laughed.

In the film by Oscar-winning writer-director James L. Brooks, Reese stars alongside Owen Wilson and Paul Rudd who she claims were equally in awe of Nicholson.

“I think Owen and Paul and I were all pinching ourselves every day we worked with him,” she joked.

Paul and Owen’s characters in the movie are pitted against each other in a love triangle with Reese’s character at the centre.

Of working with the pair, Reese said: “They’re just guys, they’re really funny you know, Owen tells funny jokes.”

She added: “It’s nice to come to work and be able to laugh and have people around you that are just inherently funny.”