In this work we present a study on the effect of the aggregation on the optical properties of star-shaped molecules. We analyzed the modification of the absorption and fluorescent properties of a 1,3,5-tristyrylbenzene core due to the formation of diverse aggregates. The nature of the aggregates in solution was investigated by different spectroscopic techniques such as electronic absorption, steady-state fluorescence, fluorescence anisotropy, time-resolved fluorescence, small-angle X-ray scattering, and dynamic light-scattering spectroscopy. In order to simulate the molecular arrangement of the aggregates, the structure and electronic properties of different clusters formed by stacking of star-shaped molecules were studied by means of density functional theory calculations. The theoretical insight was performed in the gas phase as well as in solution through the polarizable continuum model, and both linear response and state-specific polarization schemes were applied. In the solid state, high quantum yields of up to 0.51 were measured for a 1,3,5-tristyrylbenzene derivative. Finally, the morphological properties of different solid samples were analyzed by differential scanning calorimetry, as well as scanning and transmission electron microscopies.