A facile template-free hydrothermal method was successfully developed for the controlled synthesis of ultrathin α-quartz nanoplates (NPLs) for the first time. Analyses of the α-quartz NPLs revealed the characteristic anisotropic nanostructures of highly crystalline α-quartz with an average lateral size and thickness of 1.14 ± 0.32 μm and 7.7 ± 0.6 nm, respectively. Importantly, efficient extraction of highly valuable chemicals such as astaxanthin (ATX) from the microalgal cells of Haematococcus pluvialis (H. pluvialis) was accomplished by lacerating the cell walls using the ultrathin α-quartz NPLs under mild ultrasonication. The incorporation of α-quartz NPLs enhanced the ATX extraction efficiency significantly (99%, 18.0 ± 0.6 mg ATX/g cell) when coupled with 5 min of ultrasonication. The dosage of α-quartz NPLs (800.0 mg/L) for maximum ATX extraction was reduced substantially to only 8% of the nanomaterial dose used in the extraction controls. The enhanced extraction efficiency and dosage were explained by the role of the structural anisotropy of α-quartz NPLs in multiple phase separation-extraction processes. This work provides a novel, facile, and economical route for the synthesis of uniform ultrathin nanoplates, offering a new material for the highly efficient harvesting of chemical products from various microalgal biorefinery processes.