We synthesized hierarchically branched silver nanostructures (HBAgNSs) with distinctive morphologies and optical properties using non-ionic triblock copolymers under a variety of conditions. The synthetic conditions in terms of the critical micelle concentration (CMC) and temperature (CMT) are judiciously controlled to determine how the polymers in the form of micelles or unimers play a significant role in the growth of the nanostructures. The surface of the silver nanostructures can be densely functionalized with DNA, which is further utilized for the multiplexed colorimetric detection of three DNA targets in conjunction with plasmonic nanoparticle probes.