Endosidin1 is a cell-permeable chemical probe that selectively disrupts endocytic trafficking of specific plasma membrane cargo, including the brassinosteroid receptor BRI1 and the auxin transporters PIN2 and AUX1. At micromolar concentrations, it induces rapid agglomeration of these proteins into distinct endomembrane compartments called "endosidin bodies," defined by the TGN/endosomal markers SYP61 and VHA-a1, while leaving other membrane proteins like PIN1 and PIN7 unaffected. Treatment with Endosidin1 inhibits brassinosteroid-responsive gene expression and confers a brassinolide-insensitive root growth phenotype, yet it does not alter auxin signaling. This makes Endosidin1 a valuable tool for dissecting early endosomal sorting pathways and for studying the regulatory mechanisms of plant hormone receptor trafficking.