Officers said they were alerted to reports early Saturday of the man climbing the wall to get into the Royal Mews, which backs onto the Palace garden.
“At no point did the man enter Buckingham Palace or the palace gardens,” according to a statement from Metropolitan police.
The Royal Mews is a collection of stables displaying royal carriages, and is home to the Gold State Coach.
The location is responsible for all road travel arrangements for King Charles and members of the Royal Family.
Police say the man, 25, was later detained outside the stables in the Royal Mews and arrested for trespassing.
He was taken into custody.
It is not the first time intruders have broken into royal premises.
The most famous security breach was in 1982, when Michael Fagan scaled a Buckingham Palace drainpipe and broke into the Queen’s bedroom where she was sleeping.
He reportedly sat on the bed and chatted to the monarch before he was arrested.
The incident was later recreated in the Netflix series The Crown.