Nanosized organosilica particles with tunable morphology are of great interest for versatile applications because of their enhanced properties. However, it is still a great challenge to control the morphology during fabrication of organosilica nanoparticles (NPs). In this study, a facile approach based on flash nano-precipitation (FNP) technique is presented, which achieves an efficient fabrication of organosilica NPs with controllable morphology by utilizing an amphiphilic block copolymer poly(2-(dimethylamino) ethylmethylacrylate-b-poly(epsilon-caprolactone) (PDMAEMA-b-PCL) as the stabilizer. Such a preparation process is performed in a multi-inlet vortex mixer that enables an intense mixing of the silicon precursor with the aqueous solution of a catalyst at an ultrashort time scale, leading to the formation of numerous tiny reaction droplets stabilized by PDMAEMA-b-PCL, followed by the basic-catalyzed hydrolytic condensation. Interestingly, by controlling the composition and mixing parameter of feeding streams involved in the FNP process, golf ball-like, cubic, bowl-like, and hollow organosilica NPs can be easily obtained. The resultant NPs show a narrow size distribution and are expected to find potential applications in various fields, such as nanomedicine, nanocatalysts, and adsorption separation.