The group posted a statement to announce that they would not be appearing at the Northside Festival in Denmark on Friday (June 15) and Saturday (June 16) at the Hultsfred Festival in Sweden as previously scheduled.
Both cancellations were due to Marcus Mumford breaking his hand in the last several days.
The group noted that no other Mumford & Sons concerts "are expected to be affected" by Marcus's injury.
Mumord & Sons' next concert date is on Friday (June 22) at the Southside Festival in Denmark.
The group's next studio album is to be released in September.
> Mumford & Sons on new album: 'There will be no tricks'
Watch Mumford & Sons perform 'Little Lion Man' below (warning - mature content):