John Stamos ''can't wait'' to be a dad.

The 54-year-old actor is expecting his first child with wife Caitlin McHugh and admitted it feels like her pregnancy has been going on for a very long time.

John shared an old photo of himself on the set of 'Full House' with a fake baby bump covered by a white T-shirt with the words 'Bun in the Oven' written across it and wrote on Instagram: ''This is the longest 9 months of my life! #cantwait 4 #fatherhood.(sic)''

The excited dad-to-be previously revealed he has ''always'' wanted to be a father but was worried he had left it too late.

He said: ''I always wanted to be a dad. Clearly, I had to do some work on myself first. I have a youthful thing. People say, 'Oh, you look young.' You start believing you're gonna live to be 150. And then you wake up and go, 'No, man, this is it. This is not a rehearsal.' ... People would say, 'You should have a child.' I was like, 'That ship has sailed.'''

The 'Fuller House' actor - who was previously married to actress Rebecca Romijn - married Caitlin last month in an intimate afternoon ceremony at the Little Brown Church in Studio City before returning to their home in Beverly Hills for an outdoor reception.

John looked smart in a black tuxedo, while his 31-year-old bride donned a traditional white full-skirted ballgown.

But the couple's celebrations didn't go entirely smoothly as Caitlin was robbed of $165,000 worth of jewellery the day before they tied the knot.

The actress had returned to her bungalow at the Beverly Hills Hotel to discover someone had broken in and taken the accessories, which were on loan from the Neil Lane collection.

The actor proposed to Caitlin in October and announced the happy news on social media.

He posted an illustrated picture of a couple embracing at Disneyland on his Twitter account and he captioned the image: ''I asked...she said yes! ...And we lived happily ever after [ring emoji] (sic)''