Thaumatin-like proteins (TLPs), classified as pathogenesis-related protein 5 (PR-5), constitute an important component of plant defense systems. However, systematic information on the TLP family in sugar beet (Beta vulgaris) remains limited. In this study, a genome-wide investigation of TLP genes was conducted to clarify their genomic features, evolutionary relationships, and expression behavior under biotic stress. A total of 21 TLPs were identified in the sugar beet genome. These genes showed uneven chromosomal distribution and displayed marked variation in gene length, exon-intron organization, and protein physicochemical properties. Phylogenetic analysis of Arabidopsis PR-5 proteins classified the sugar beet members into multiple conserved groups, with consistent gene structure patterns within each group. Expression profiling under Sclerotinia sclerotiorum infection revealed that BvTLP09, BvTLP10, BvTLP12, BvTLP04, and BvTLP01 were strongly induced, whereas other PR-5 genes showed weak, unchanged, or reduced transcriptional responses. Reanalysis of RNA-seq data from beet cyst nematode infection further demonstrated distinct expression patterns between resistant and susceptible varieties at early and late infection stages, indicating dynamic and genotype-dependent regulation of PR-5 genes. This study expands current knowledge of the PR-5 gene family in sugar beet and provides a basis for future functional studies on their roles in pathogen-responsive pathways.