Abstract: Sweet potato (Ipomoea batatas (L.) Lam.) is a major global food crop with a complex hexaploid genome, whereas its wild diploid relative I. trifida (Kunth) G. Don possesses a simpler genomic architecture that serves as a valuable reference for elucidating gene function and structural evolution in I. batatas. Glutamate decarboxylase (GAD), a key enzyme in the γ-aminobutyric acid (GABA) branch biosynthesis pathway, catalyzes the conversion of glutamate to GABA and plays a crucial role in plant stress responses. In this study, 15 ItfGAD genes were identified in the I. trifida genome, designated ItfGAD1 to ItfGAD15 based on their chromosomal location. Bioinformatic analyses revealed that most ItfGAD proteins were acidic, with amino acid (aa) lengths ranging from 476 to 537 and isoelectric points (pI) between 5.69 and 8.7. Secondary structure prediction indicated that α-helices and random coils predominated. Subcellular localization analysis suggested that 11 ItfGAD proteins were cytoplasmic. Multiple sequence alignment showed that all ItfGAD proteins contained a highly conserved PLP-binding domain, and phylogenetic analysis classified them into four distinct evolutionary branches. The number and distribution of conserved motifs, exons, and introns varied considerably among different ItfGADs, suggesting functional diversification. Transcriptomic and qRT-PCR analyses demonstrated tissue-specific and stress-responsive expression patterns. ItfGAD4 exhibited the highest expression in stems, ItfGAD5 and ItfGAD14 were predominantly expressed in roots, and ItfGAD6, ItfGAD9, and ItfGAD12 exhibited maximal expression in leaves. Under salt and drought stress, response times, expression peaks, and variation trends differed among genes in root and leaf tissues, indicating distinct regulatory roles in abiotic stress adaptation. Collectively, these results provide a comprehensive framework for understanding the biological and regulatory functions of the ItfGAD gene family and offer novel insights into the molecular mechanisms that mediate responses to abiotic stress tolerance in I. trifida.