Herein, we demonstrate that double hydrophilic block copolymers can be used for the preparation of photocatalytically active organic/inorganic hybrid micelles. This is realized by immobilization of CdS nanoparticles for photocatalytic water splitting within well-defined poly(2-iso-propyl-2-oxazoline)-block-poly(2-acrylamido glycolic acid) (PiPrOx-b-PAGA) block copolymers. The prepared PiPrOx-b-PAGA/CdS hybrid nanostructures were characterized regarding morphology, structure, and optical properties by UV/Vis and photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray photoelectron spectroscopy (XPS). Our results confirm spherical inorganic-organic micelles containing ultra-small CdS nanoparticles with photoluminescent character within the core. Afterwards, these hybrid nanostructures were used for photocatalytic H2 production in the presence of triethanol amine (TEOA) as sacrificial reagent in water under visible-light illumination (λ ≥ 470 nm), revealing 18-fold increased activity compared to bare CdS nanoparticles. The enhanced photocatalytic activity can be attributed to several factors, such as 3D confinement within micellar nanostructures, the presence of ultra-small CdS nanoparticles, or an improved stability of CdS nanoparticles within the micellar core. Overall, we demonstrate that double hydrophilic BCP can be an interesting platform for the formation of photocatalytically active micellar nanostructures, leading to materials with potential relevance for photocatalysis.