The London Metropolitan Police were called to the Rose and Crown on Farnborough Way, Orpington. They said they were called to the pub at 7.05pm by the London Ambulance Service.
The Met Police introduced a crime scene in place in the pubs car park and on Farnborough Way.
A video posted by London 999 Feed showed Farnborough Way cordoned off as officers investigate.
Diversions are in place on the roundabout leading to the pub.
One resident said to London 999 Feed: “The pub has a large back garden and is very popular with families on a Sunday.”
On Saturday, a shocking five people were left injured after three separate shootings.
The horrific events took place over seven hours, with two men injured in Hackney.
Two more were shot in Brixton and a fifth was left wounded in Croydon after the shooting spree.
Sadiq Khan said in 2019 that he “lays awake at night” thinking about the horrific crime in the capital.
He said: “How many Londoners will be the victims of violence in the coming days?
“How many women will have to suffer sexual assault or domestic violence? (…) And what more can we do to bring this suffering to an end?”
Bromley Borough MPS has issued an appeal for more information over the Orpington stabbing.
Witnesses have been asked to Call 101 & quote CAD 6880/02AUG or contact Crimestoppers with more information.