The City of London will introduce a 20mph (32kph) speed limit as part of its Road Danger Reduction Plan.
A 10 per cent reduction in road casualties had been estimated, the council said in a press release.
The change also would build on the work done by the City of London Corporation to improve cycling safety in the City and benefit pedestrians significantly.
The change was supported by the Mayor of London, Transport for London, and the City of London Police, it said.
Journey times were estimated to increase by only minutes.
It would have minimal impact on air quality, an investigation by City Authorities had shown.
All the surrounding City boroughs, with the exception of Westminster, already had adopted a 20mph limit and it had been shown to be effective in reducing both the number and severity of collisions.
The speed limit reduction was approved by the City of London Court of Common Council on September 12, the press release said.
Chairman of policy and resources Mark Boleat said: “As an international business hub, the City plays host to a large number of commuters every day.
“Steps that make it safer for City workers and reduce the number of tragic deaths are to be welcomed.”
Michael Welbank, chairman of the planning and transportation committee, said: “I am delighted this proposal has been passed.
“The City of London’s street usage has changed dramatically over the last 10 years, with the number of cyclists tripling.
“The Corporation has adopted a Road Danger Reduction Plan containing a wide range of measures.
“The 20 mph speed limit for the City is not the panacea but a further step in reducing casualties.”