Valerie and John Dunkley, now aged 60 and 70 respectively, opened the restaurant, which includes cocktail and coffee lounges in 1920 railway carriages, in 1984.
John Dunkley told the Northampton Chronicle & Echo that the time was now right to close as although their son and daughter and four of their six grandchildren had worked in the restaurant, they are all now involved in other careers.
"Partly it's the economic climate, which has made things hard in the last few years, but we think now is the right time in our 70th years.
"I feel very sad because the staff have been so loyal and we've had some great times. Hopefully people have enjoyed themselves like we have."
The restaurant is now expected to be sold as a residential property.