Developing artificial light‐harvesting scaffolds with a cascade energy transfer process is significant for better understanding of photosynthesis. Here, we report [3 3] self‐assembled PtII fluorescent macrocycles (3 a and 3 b) as light‐harvesting platforms with cascade energy transfer. The PtII macrocycles aggregate into nanospheres and show emission‐enhancement characteristics upon increasing water content in acetone medium. These aggregates (3aa and 3ba) serve as energy donors when mixed with the hydrophobic dye Eosin‐Y (ESY). In the presence of a second dye, Nile Red (NiR), an unusual sequential two‐step energy transfer takes place from the macrocycles to NiR. In this case, ESY acts as a bridge in the relay mode. Additionally, a unique strategy to control such an energy transfer process by tuning the chain length of the alkyl group attached to the periphery of the macrocycles is demonstrated.