The nature and relative strength of the intermolecular interactions responsible for the behavior of PAMAM dendrimers as encapsulating agents were investigated in neutral aqueous solution through optical spectroscopy methods. In order of relative importance, we found electrostatics, hydrogen bonding, and interactions mediated by aromatic moieties in the guest molecules to be the main drivers to complex formation in these systems. Insights were gained by studying the binding of small targeted organic anions to these dendrimers (G3-G6) by an indicator displacement method, monitoring spectral signals (absorbance, fluorescence emission, and anisotropy). This study contributes to a more complete understanding of the fundamental interactions involved when these hyperbranched polyelectrolytes function as supramolecular hosts, a role they commonly assume in many of their applications e.g. as drug delivery vectors.