The closure is being forced upon the group as the landlord of the building, Cheval Property Holding Limited, plans to redevelop the block it's located in.
Spaghetti House, which celebrates its 60th anniversary this year, said it continues to look for another site in Knightsbridge to trade from. The restaurant's 19 staff members will be offered positions at its 11 other branches in London.
Chief executive and managing director Luigi Lavarini said the group was sad to lose a successful branch and one with such a 'rich history'. The branch was the scene of a five-day siege in 1975 following an attempted armed robbery and the company's head office was located above for 16 years.
"However,it is also a time to celebrate an incredible 46 years of business in Knightsbridge, something that arguably very few restaurants can do," he said. "Over the years customers have become friends, we will not lose them altogether because they will visit our nearby branches, whilst we continue to look for an alternative location in the area."