Nanoparticle encapsulation within micelles has been demonstrated as a versatile platform for creating water-soluble nanocomposites. However, in contrast to typical micelle encapsulants, such as small molecule drugs and proteins, nanoparticles are substantially larger, which creates significant challenges in micelle synthesis, especially at large scale. Here, we describe a new nanocomposite synthesis method that combines electrospray, a top-down, continuous manufacturing technology currently used for polymer microparticle fabrication, with bottom-up micellar self-assembly to yield a scalable, semicontinuous micelle synthesis method: i.e., micellar electrospray. Empty micelles and micellar nanocomposites containing quantum dots (QDs), superparamagnetic iron oxide nanoparticles (SPIONs), and their combination were produced using micellar electrospray with a 30-fold increase in yield by weight over batch methods. Particles were characterized using dynamic light scattering, transmission electron microscopy, and scanning mobility particle sizing, with remarkable agreement between methods, which indicated size distributions with variations of as little as ~5%. In addition, new methodologies for qualitatively evaluating nanoparticle loading in the resultant micelles are presented. Micellar electrospray is a broad, scalable nanomanufacturing approach that should be easily adapted to virtually any hydrophobic molecule or nanoparticle with a diameter smaller than the micelle core, potentially enabling synthesis of a vast array of nanocomposites and self-assembled nanostructures.