Actor Leonardo DiCaprio unwittingly scared a shop assistant when he walked into a jewelry store wearing dark glasses and a hooded top - she thought he was a robber.

The Titanic star is currently in Australia filming Baz Luhrmann's The Great Gatsby and he took time out of his hectic schedule to visit Sydney's Family Jewels shop.

A sales assistant working behind the counter, who has been named only as Linda, feared the worst when she saw two burly bodyguards enter the store, before DiCaprio walked in disguised in shades, a hood, and a baseball cap.

The shop worker was about to notify owner Kane Kefkens, believing the three men were robbers, but she suddenly recognized the actor.

Kefkens tells the Sydney Daily Telegraph's Confidential, "Linda was working on her own and I was next door grabbing a coffee. Linda was serving a customer when the two big bodyguards approached. The customer sees what's happening and says, 'This doesn't look good'.

"Linda sent the customer next door to get me, thinking the shop is about to be robbed by these guys. By the time I get in there Linda has realized who she was serving and let me know everything was all right."