Fluorescence probes are usually employed to analyze pharmacokinetics of drug carriers; however, this method using usual probes is not suitable to monitor drug carriers in detail because fluorescence spectra do not change by the disruption of drug carriers. In this study, pyrene-fatty acid conjugates were investigated as probes to monitor the state of drug carriers in real time. 1-Pyrenemethanol was conjugated with fatty acids, such as lauric acid, stearic acid, and behenic acid, and the conjugates were stirred in ethanol, resulting in the formation of submicron particles; these particles exhibited excimer emission. When J774.1 and Colon 26 cells were treated with these particles, the associated fluorescence spectra shifted from excimer emission to monomer emission. Moreover, the degree of change was controlled by the type of fatty acid. These results support the design of drug carriers that can be used to monitor pharmacokinetics in real time and to control the disruption time.