Fluorescent small molecules have received considerable attention due to their potential for chemosensing and bioimaging. A conventional strategy for probe development is a target-oriented approach based on known molecular recognition mechanisms for individual analytes. However, sophisticated rational design does not always guarantee the applicability of probes in complex biological systems. Therefore the speed and the scope of sensor development has been limited. To overcome these limitations, diversity-oriented fluorescence library approaches have been applied to develop new fluorescent probes in the absence of knowledge about the target recognition mechanism. This review summarizes recent advances in fluorescent probe development facilitated by diversity-oriented library approaches.