The classification and phylogenetic relationships within the Phaseoleae tribe (Leguminosae) have consistently posed challenges to botanists. This study addresses these taxonomic intricacies, with a specific focus on the Glycininae subtribe, by conducting a comprehensive analysis of the highly conserved plastome in Amphicarpaea edgeworthii Benth., a critical species within this subtribe. Through meticulous genomic sequencing, we identified a plastome size of 148,650 bp, composed of 128 genes, including 84 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Comparative genomic analysis across seven Glycininae species illuminated a universally conserved circular and quadripartite structure, with nine genes exhibiting notable nucleotide diversity, signifying a remarkable genomic variability. Phylogenetic reconstruction of 35 Phaseoleae species underscores the affinity of Amphicarpaea with Glycine, placing Apios as a sister lineage to all other Phaseoleae species, excluding Clitorinae and Diocleinae subtribes. Intriguingly, Apios, Butea, Erythrina, and Spatholobus, traditionally clumped together in the Erythrininae subtribe, display paraphyletic divergence, thereby contesting their taxonomic coherence. The pronounced structural differences in the quadripartite boundary genes among taxa with unresolved subtribal affiliations demand a reevaluation of Erythrininae’s taxonomic classification, potentially refining the phylogenetic contours of the tribe.