Enzyme assays are receiving more and more research and application interest because of the rapidly increasing demands of clinical diagnosis, environmental analysis, drug discovery, and molecular biology. Water-soluble light-harvesting conjugated polymers (CPs) coordinate the action of a large number of absorbing units to afford an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. This Feature Article highlights recent developments of water-soluble CPs for fluorescent assays of enzymes. Different signal transduction mechanisms, such as electron transfer, fluorescence resonance energy transfer (FRET), and aggregation or conformation changes of CPs, are employed in these assays according to the dissimilar nature of enzymes. Potential challenges and future research directions in these approaches based on CPs are also discussed.