The vandalism was carried out by members of the Palestine Action organization, which has previously concentrated its campaign on the UK business of Israel-based defense contractor Elbit.
Pictures on X featured broken glass and extensive graffiti on a number of bank branch doors.
Branches in London, Birmingham, Bristol, and Edinburgh were among the places targeted.
Members of the environmental protest group Shut the System were also among the campaigners.
Barclays was charged by Palestine Action of having financial ties to both the fossil fuel industry and the Israeli arms trade.
Shut the System posted on its X account, stating: “For the sake of all life on Earth.”
Broken windows and glass fragments gleaming on pavements serve as a constant reminder of the shattered dreams for a future that is habitable for all living things.”
It is acknowledged that while 15 locations sustained damage, nobody was harmed.
The impacted branches are closed at this time.
“We provide vital financial services to US, UK, and European public companies that supply defense products to NATO and its allies,” a Barclays spokeswoman stated.
“Barclays does not make these companies’ investments directly.
The UK government has made it apparent that supporting defense companies is consistent with environmental, social, and governance (ESG) issues.