Hydrogelators are crosslinked polymeric networks that are capable of holding large amounts of water by surface tension. High-water absorption capacity makes hydrogels readily biocompatible and, thus, more attractive for medical applications. The objective of the present in vitro study was to test supramolecular hydrogelators for multiple biomedical applications: bacterial- and cancer-related diseases. Four naphthalene-tripeptides and their D-enantiomers were synthesized using an Fmoc Solid Phase Peptide Synthesis strategy and were tested for their activity on normal and cancer cells as well as bacteria. Here, the D-enantiomer of alanine containing tripeptides at a concentration of 0.25 wt% inhibited the growth of Staphylococcus epidermidis. Moreover, cytotoxicity assays showed that naphthalene containing tripeptides possessing α-aminoisobutyric acid (Aib, U) between the two phenylalanine groups (i.e., NapFUF) selectively decreased against melanoma cancer cell viability at 0.25 wt% compared to controls (no additives) over a 24 h time period. These results suggest, for the first time, that naphthalene-tripeptides containing α-aminoisobutyric acid or alanine have numerous potential uses for diverse medical applications, in particular for fighting cancer and bacterial infections.