Giant invasive sacral schwannomas are rare tumors. Surgical excision is the standard treatment and total resection is performed if feasible. Advances in three-dimensional (3D) imaging technology have facilitated treatment designs of complex surgical procedures. Our aim was to evaluate virtual surgical planning, computer-aided design (CAD), and manufacturing with 3D printing technology of the customized osteotomy guiding device in giant invasive sacral schwannoma resection. A digital 3D model of the sacrum, including the giant invasive sacral schwannoma, was rendered from patient computer tomography (CT) images. The surgeon chose excision margins of the tumor. Based on the virtual surgical planning, the customized guiding tool for osteotomy was designed and manufactured using the CAD and 3D printing. We used the guiding block to successfully excise a giant sacral schwannoma using only a posterior approach to achieve gross total resection. No augmented spinal instrumentation was used to prevent iatrogenic spinal instability. Clinical symptoms resolved dramatically after operation. No spinal instability occurred during follow-up. With the assistance of an image-based customized osteotomy guiding device, we achieved both goals of tumor resection and bone preservation in giant sacral schwannoma resection. With thorough surgical planning, this technology can be applied to the complex surgical procedures easily and reliably.