Clathrin-mediated endocytosis (CME) is a conserved Eukaryotic trafficking pathway that is driven by a sequentially self-assembled molecular machinery of over 50 different proteins. What protein-protein interactions regulate assembly of the endocytic machinery? I describe how the most abundant PPI domain family in CME – SH3 domains – regulate endocytic protein assembly in the budding yeast Saccharomyces cerevisiae, combining mutagenesis with live cell fluorescence microscopy. My data suggest that most SH3 domains regulate recruitment of their own SH3 protein and SH3 domains that recruit other endocytic proteins do not promote recruitment of their own SH3 protein. Furthermore, multiple SH3 domains mediate the same endocytic component, the Las17/Vrp1 complex (LVC), and interfere with each other. The SH3 interaction network coordinates LVC assembly and dissociation dynamics. My results provide a dynamic map of SH3 functions in yeast endocytosis that can help SH3 research in a broad biological and medical context to conceptualize SH3 interaction networks.