Polyethylene glycol modified diperylene bisimide (PEG-diPBI) was synthesized and applied to disperse single-walled carbon nanotubes (SWCNTs) in water. The aqueous dispersion efficiency of PEG-diPBI on SWCNTs is investigated by UV-vis, Raman spectroscopy, and transmission electron microscopy. It is found that the enhanced dispersing capability of PEG-diPBI can be attributed to the diperylene aromatic core, which can strongly interact with SWCNT via synergistic π–π and hydrophobic interactions. The dispersing solution properties are closely related to the hydrophilic part of PEG-diPBI. Moreover, the well-dispersed SWCNTs show excellent antibacterial activities.