A biocompatible hydrogel containing a hexapeptide as a key unit has been designed and fabricated. Our design construct comprises a β-sheet-rich short hexapeptide in the center with a hydrophobic long chain and hydrophilic triple lysine unit attached at the N- and C-terminals, respectively. Thus, it is this amphiphilic nature of the molecule that facilitates gelation. It can capture solvent molecules in the three-dimensional cross-linked fibrillar networks. The amphiphilic character of the construct has been modulated to produce an excellent biocompatible soft material for the inhibition of bacterial growth by rupturing the bacterial cell membrane. This hydrogel is also stable against enzymatic degradation (proteinase K) and, most importantly, offers a biocompatible environment for the growth of normal mammalian cells due to its noncytotoxic nature as observed through the cell viability assay. From the hemolytic assay, the morphology of the human red blood cells is found to be almost intact, which suggests that the hydrogel can be used in biomedical applications. Thus, this newly designed antibacterial hydrogel can be used as both an antibacterial biomaterial and a biocompatible scaffold for mammalian cell culture.