Solid polymer electrolytes (SPEs) have attracted intensive attention due to their potential applications in all-solid-state lithium batteries. Tailoring crystallization is crucial to the design of high performance poly(ethylene oxide) (PEO)-based SPEs. In this paper, we demonstrate that PEO crystal orientation in a PEO lithium electrolyte results in anisotropic ionic conductivity along and through the crystalline lamellae. This conductivity anisotropy can be further enhanced by incorporating two-dimensional graphene oxide (GO) nanosheets, which retard PEO crystallization, template the crystal orientation, and guide the ion transport, leading to highly anisotropic and conductive nanocomposite polymer electrolytes.