High-grade spondylolisthesis is a severe spinal deformity that can present in children, adolescents, and adults. Spondylolisthesis is the displacement of one vertebral body over another, and high-grade spondylolisthesis signifies a greater than 50% displacement of the vertebral body. This is a relatively rare spinal deformity and optimal management is controversial. High-grade spondylolisthesis can be treated via conservative or surgical treatment algorithms. Surgical treatment generally includes lumbar decompression with instrumented fusion in conjunction with interbody fusion. While spondylolisthesis reduction is controversial, restoring overall sagittal and spinopelvic alignment is paramount.