Shooting begins on the Finglas man's €4.7m movie next August and Dublin's Moore Street is central to the plot.
The cameras need to roll day and night which would not have been possible on the street without closing it to the public for several weeks. The solution was to recreate the famous street at Pinewood Studios.
"It sounds mad but the only day we could film on the real Moore Street in Dublin was on a Sunday," explained the award-winning comedian.
"That was no good as we needed the street for weeks on end so the team are building their own Moore Street from pictures I've taken. They asked me how long it should be and I told them I didn't care as long as the number 83 Moore Street is in the film.
"That's where my granny was born", he added.
The new movie follows a successful book, stage show and sitcom featuring the day-to-day escapades of Mrs Brown and her sons.
O'Carroll picked up a Bafta for his comedy creation earlier this year.