Dendrimers are regularly branched three-dimensional macromolecules, whose properties are dependent on the numbers of generation and branch units, along with the structures of building blocks, surface groups, and core modules.1 Site-selective positioning of functional groups in dendritic architectures is expected to induce cooperative phenomena that may lead to a significant enhancement of certain functions. Examples of such cooperative phenomena with dendritic macromolecules have been reported for catalysis, 2 molecular recognition and inclusion,3 and light harvesting.4 We are motivated to explore the potential utility of such a cooperative phenomenon for sensory applications. Here, we report the synthesis of a series of dendritic macromolecules functionalized with multiple zinc porphyrin units (Chart 1) and highlight a clear cooperative effect on chiroptical sensing of an asymmetric ligating molecule.