A biocompatible drug delivery nanocarrier with cellular and subcellular targeting properties can greatly enhance the therapeutic effect towards various diseases. Here, we report polyaspartamide based functional polymeric nanoparticles as drug delivery carriers for targeting at the cellular and subcellular length scale. The polymeric nanoparticle has a polyaspartamide backbone with both octadecyl and dopamine functional groups and produces polymeric nanoparticles in water with the exposed dopamine. This polymeric nanoparticle has good encapsulation efficiency for hydrophobic drugs and offers cellular delivery of the drug into dopamine receptor positive human colon adenocarcinoma cells. Using this approach three different drugs (e.g. curcumin, camptothecin and doxorubicin) are selectively delivered to human colon adenocarcinoma cells. Subcellular imaging study shows that the delivered drugs retain their ability to target subcellular organelles and thus curcumin targets mitochondria and doxorubicin targets the nucleus. This polymeric nanoparticle can be used as an alternative drug delivery carrier for in vitro and in vivo applications.