It is the first time the flow has stopped since an explosion on the Deepwater Horizon rig on 20 April.
The company is now conducting a critical pressure test on the well.
Watch the process here
It will monitor the pressure in the well to see if there are any leaks further down the pipeline.
BP senior vice president Kent Wells said: 'I'm very excited to see no oil flowing into the Gulf of Mexico.'
However, BP has warned that the latest development does not mean the flow has been stopped permanently.
That will not happen until a relief well is completed next month.
BP chief operating officer Doug Suttles said: 'I think it's an encouraging sign. In a couple of more days it may even be more encouraging, but no celebrations.
'If you go talk to these people that live here, celebration is the wrong word.'
Between 35,000 and 60,000 barrels of oil a day have been leaking from the well since April, threatening wildlife along the coastlines of five US states.
US President Barack Obama welcomed the news of the capped well as 'a positive sign', but cautioned: 'We're still in the testing phase.'
The disaster has so far cost BP almost €2.78bn and compensation claims from residents of the region could reach ten times that.
