Supramolecular aggregates of organic dyes through noncovalent interactions have attracted great interest because they exhibit collective optical and excitonic properties. We report the formation of spherulitic J-aggregates from the coassembly of lithocholic acid (LCA) and 3,3'-diethylthiacarbocyanine iodide (DiSC(3)) in ammonia solution. Each spherulite contains a core, which serves as a nucleus for the growth of radially oriented J-aggregate fibrils. We find that the growth of spherulitic J-aggregates exhibits a sigmoidal kinetic curve with an initial lag time, followed by a period of rapid growth and a finally slow approach to equilibrium.