Understanding how climate regimes respond to ongoing warming is critical for managing water resources and environmental systems in arid and semi-arid regions. This study investigates observed climate-type transitions across Iran over the past seven decades using the Ko & uml;ppen-Geiger classification applied to long-term observations from 279 synoptic stations. To ensure robust temporal coverage, stations were grouped by data availability (1951-2024, 1976-2024, 2001-2024), and climate types were evaluated across multiple sub-periods to capture spatiotemporal shifts. Trends in annual mean temperature and precipitation were assessed using the Mann-Kendall test and Sen's slope estimator. The results reveal a systematic shift toward warmer and drier regimes, with climate-type transitions identified at 27% of long-record and 18% of mid-record stations, predominantly from temperate and cold climates to arid types. Changes are most pronounced in central, eastern, and northwestern Iran and coincide with significant warming and widespread precipitation declines, indicating warmingdriven aridification as the dominant mechanism. A significant association between latitude and climate-type transitions highlights enhanced sensitivity in northern transitional drylands. Overall, the findings demonstrate that ongoing atmospheric warming is actively reshaping Iran's dryland climate regimes, with important implications for hydroclimatic stress, water scarcity, and environmental sustainability in arid and semi-arid regions.