negatively regulates actin nucleation regulation of actin nucleation negative regulation of actin nucleation down regulation of actin nucleation GO:0051126 inhibition of actin nucleation Any process that stops, prevents, or reduces the frequency, rate or extent of actin nucleation, the initial step in the formation of an actin filament in which actin monomers combine to form a new filament. down-regulation of actin nucleation biological_process downregulation of actin nucleation negative regulation of cytoskeleton organization biological regulation negative regulation of supramolecular fiber organization