Abstract: The montane rainforests of Ethiopia are the only known centres of origin and genetic diversity for Coffea arabica. However, the remnant coffee forest environments with the spontaneously grown wild coffee populations are under continuous threat of genetic erosion, largely due to anthropogenic activities. The study was conducted with the objective to investigate stomatal characteristics in Arabica coffee accessions under contrasting shade regimes at Jimma (7°46’ N and 36°0’ E, 1750 m), southwestern Ethiopia. For this, two shade levels (full sunlight and moderate shading) and twelve-coffee germplasm accessions were arranged as main and sub-plot treatments in a split-plot design with three replicates. The results depicted that stomata were sparsely distributed and had elliptical guard cells with pores randomly oriented pattern in Arabica coffee leaf. Maximum and minimum average stomatal densities were determined in full sunlight and moderate shade conditions, respectively. In addition, the stomatal area index was significantly higher in sun-exposed than in shaded leaves. The lowest and highest values were determined for the Harenna and Yayu accessions, respectively. The interaction between season and radiation was significant (p<0.05) on the frequency of stomata. The contrasting shade levels had significant influence on the density of stomata in both wet (p<0.05) and dry (p<0.001) seasons. Accordingly, higher stomatal frequency was recorded in dry as compared with wet season, though the range differed among the genotypes. Overall, stomatal size values followed the rainfall gradient with the order: Harenna>Bonga>Berhane-Kontir>Yayu coffee genotypes. The results would demonstrate that coffee accessions in drier Harenna areas may be more productive under higher radiation when soil moisture is sufficient. This underlines the need to consider stomata traits in identifying and developing suitable coffee cultivars against the changing environments.