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Annual and perennial life‐history strategies have evolved repeatedly across angiosperms, yet the genomic and environmental underpinnings of these transitions remain poorly understood, particularly in grasses. Here, we generated de novo transcriptomes from 82 accessions representing 22 Hordeum species, including barley and identified 257 single-copy orthologs present in all accessions to infer a robust phylogeny of the genus. By combining phylogenetic network inference with ABBA-BABA tests, we detected four well-supported cases of interspecific hybridization, three of which coincided with major long-distance dispersal events across continents. Comparative climatic niche analysis indicated that annual Hordeum species tend to inhabit environments characterized by higher temperatures and greater interannual temperature variability, as well as increased human disturbance, compared to their perennial relatives, although no consistent differences in precipitation were observed. Using our well-resolved phylogeny as a comparative framework, we analyzed patterns of selection, gene expression, and gene copy-number variation to uncover genomic changes associated with life-history strategy while accounting for phylogenetic non-independence. These analyses yielded 174 candidate genes spanning a wide range of biological functions, suggesting that the genetic architecture underlying life-history evolution is more complex than previously assumed. Candidate genes grouped into six major functional categories, with the most prominent being signal transduction and development, which includes regulators of flowering, dormancy, and meristem activity, metabolic and biosynthetic processes related to carbon allocation and storage, and stress response and defense, reflecting the long-term resilience of perennials compared to the accelerated growth strategies of annuals. Together, our study not only reconstructs the evolutionary history and climatic niche differentiation of Hordeum species but also demonstrates that convergent life-history evolution is driven by multifaceted and functionally diverse genetic mechanisms.