Mitofusins (MFNs) promote fusion-mediated mitochondrial content exchange and subcellular trafficking. Mutations in Mfn2 cause neurodegenerative Charcot-Marie-Tooth disease type 2A (CMT2A). We showed that MFN2 activity can be determined by Met³⁷⁶ and His³⁸⁰ interactions with Asp⁷²⁵ and Leu⁷²⁷ and controlled by PINK1 kinase–mediated phosphorylation of adjacent MFN2 Ser³⁷⁸. Small-molecule mimics of the peptide-peptide interface of MFN2 disrupted this interaction, allosterically activating MFN2 and promoting mitochondrial fusion. These first-in-class mitofusin agonists overcame dominant mitochondrial defects provoked in cultured neurons by CMT2A mutants MFN2 Arg⁹⁴→Gln⁹⁴ and MFN2 Thr¹⁰⁵→Met¹⁰⁵, as demonstrated by amelioration of mitochondrial dysmotility, fragmentation, depolarization, and clumping. A mitofusin agonist normalized axonal mitochondrial trafficking within sciatic nerves of MFN2 Thr¹⁰⁵→Met¹⁰⁵ mice, promising a therapeutic approach for CMT2A and other untreatable diseases of impaired neuronal mitochondrial dynamism and/or trafficking.