Justin Bieber and Selena Gomez crashed a wedding over the weekend.

The couple were having a romantic dinner date at a restaurant on Malibu Beach when they heard Justin's music playing at some nearby nuptials.

So they ventured over, leaving the bride and groom and their guests stunned.

A source said: "Unbeknownst to all of the guests, Justin Bieber and his girlfriend Selena Gomez were just done eating at a restaurant up the road from the Adamson House estate and had decided to take a stroll down the beach. I guess he heard his song play and decided to crash the wedding party to check the scene out. He was cool enough to make a cameo, which surprised all of the wedding guests."

The 'Baby' singer also congratulated the newlyweds, Rob and Jeanine McCool, on tying the knot and posed for pictures with the couple and guests.

The source added to PerezHilton.com: "He even took the microphone, congratulated the newlywed couple, and said a few nice words, while posing for a series of pictures with his fans. That was one of the coolest and nicest things a person of his celebrity can do, and it certainly made a memorable night for the newlywed couple Mr. and Mrs. Rob and Jeanine McCool."