Plastic pollution poses a critical global environmental challenge, and within this context, nanoplastics (NPs), the smallest plastic fragments, remain poorly understood. The progress in studying NP toxicity and developing analytical methods highly depends on access to well-defined NP materials. Herein, a straightforward and ecofriendly method for fabricating NP particles and fibrils using polymer blends as templates is presented. The process began with blending plastics with a water-soluble polymer (polyvinyl alcohol (PVA)), followed by the dissolution of the PVA matrix in water and the isolation of the NPs through a two-stage filtration process. NP materials from three widely used plastics, polyethylene, polypropylene, and polystyrene, were prepared, underscoring the versatility of this method. The resulting NPs were primarily submicron in size, and their size distribution was tuned by varying the blend ratio. Furthermore, by incorporating a stretch operation during the extrusion, the NP shape could be varied, enabling the fabrication of NP fibril materials. This method, which does not rely heavily on specialized equipment and avoids the use of harsh solvents, offers a viable and eco-friendly approach to fabricating NP samples suitable for a broad range of research applications.