Bertolotti’s syndrome refers to a condition characterized by anatomical variations involving one or more lumbosacral articulations, typically featuring additional articulations between L5 transverse process and sacral ala bone (known as lumbosacral transitional vertebrae, LSTV). This syndrome is also known as far-out syndrome (FOS) and commonly associated with lumbosacral pain and may occasionally manifest with unilateral leg pain or neurological symptoms. For many years, endoscopic spinal surgery has become possible to treat many degenerative spinal diseases. In particular, the development of unilateral biportal endoscopic (UBE) surgery has largely replaced the conventional surgery. UBE surgery shows a more magnified view compared to a microscope and has a clear-bloodless surgical field and an unrestricted use of conventional surgical instruments. This chapter introduces the detailed technique of Bertolotti’s syndrome decompression using UBE. We hope that surgeon will learn this technique and treat the Bertolotti’s syndrome sufficiently.