The steady-state fluorescence emission from 12-(1-pyrenyl)dodecanoic acid (PyDDA) in aqueous, organic, and micellar solutions has been studied as a function of pH and concentration of PyDDA and selected surfactants. The pH-dependent aggregation of PyDDA in aqueous solution shows strong aggregation of the acid molecules through H-bonding and hydrophobic interaction of alkyl chains under suitable conditions, manifested as blue shifts in the excimer emission. Emission studies in dodecanoate solution responded to the premicellar aggregation phenomenon. Possible implications of this study to solid-liquid interfacial probing are discussed.