This study is motivated by quantifying potential evapotranspiration (PET) evolution under climate change in the Arabian Peninsula. It implements climatic data in the Penman approach to investigate the development in PET values through the 21st century. Climatic simulations were obtained from 10 global circulation models in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Analysis showed that PET losses are projected to increase between 0.18 mm and 0.96 mm/year through the end-21st century, under the shared socioeconomic pathway SSP5-8.5. The warming trend over the Arabian Peninsula seems to be the primary driver of PET increases. These results imply severe consequences for the Arabian Peninsula countries, which have indeed a very high water deficit. Therefore, sustainable management and augmentation of water resources should be prioritized in future agendas.