This work reports the preparation of ordered arrays of gold nanoparticles by sonochemically enhanced borohydride reduction of precursor lithium tetrachloroaurate (LiAuCl) incorporated into the core of polymeric micelles formed from amphiphilic copolymers of polystyrene (PS) and poly(ethylene oxide) (PEO). The copolymers were prepared with varying styrene block lengths from a PEO macroinitiator by atom transfer radical polymerization (ATRP). UV/visible spectroscopy was used to confirm the formation of elemental gold. The effect of sonication time on the appearance of the gold nanoparticles was determined and showed that the absorbance first increased as the nanoparticles formed but decreased at longer times, presumably as a result of a degree of agglomeration. Transmission electron microscopy revealed the morphology of the nanocomposites which confirmed that micellar polystyrene-block-polyethylene oxide is an excellent vehicle for the formation of well-defined films containing nanoparticulate gold. However, we report for the first time that care must be taken to optimize the preparation time to obtain the desired particle sizes because this parameter is very sensitive to the duration over which sonication is carried out.