John Krasinski had to convince customs agent he's married to Emily Blunt

John Krasinski says he's no stranger to the idea that he "married up" to actress Emily Blunt, and has revealed the hilarious moment he had to convince a UK customs officer of their relationship.

The Office star stopped by The Tonight Show, and told Jimmy Fallon that while visiting Blunt on the set of "small Indie film" Mary Poppins, he had a less than pleasant experience.

"It was going great, the customs, the whole experience. And then I hit this guy who was about my age," Krasinski, 38, recalled. "He looked like he was ready to get a little surly with me.

"He said, 'It says here that you're an actor. Would I know you from anything?' And I went, 'You know, we re-did the UK version of The Office,'" he shared.

"Strike one".

But it Krasinski said it was when he told the agent he was married to Blunt that things really took a turn for the worse.

"And then he says, 'Who are you visiting here?' And I was like, 'My wife,'" said the star. "He says, 'Oh, is she an actress? Would I know her?' And I said, 'I don't know man, her name's Emily Blunt.' And he goes 'YOU?'"

As the audience laughed, Krasinski said the agent angrily stamped his passport and told him to "Go. Just go.'"

Krasinski and Blunt star alongside each other in the upcoming thriller A Quiet Place, which hits New Zealand cinemas Thursday.

Newshub.