Cucumber (Cucumis sativus) is a widely cultivated plant in the family Cucurbitaceae that is grown as greenhouse crop in Oman. During a recent survey for begomoviruses, whitefly infestation was observed in two greenhouses of cucumber in the Barka region. Plants were exhibiting a foliar yellow mosaic and crumpling, symptoms typical of begomovirus infection, with an incidence of 50 to 60%. Leaves from four symptomatic plants were collected, two plants from each greenhouse, as well as leaves from two apparently healthy (symptomless) plants, one from each greenhouse. Electron microscopy analysis of negatively stained sap samples showed the presence of geminate (twinned quasi-icosahedral) particles of ∼18 to 20 × 30 nm in samples from symptomatic but not nonsymptomatic plants, suggesting the presence of a geminivirus. Based on the results of PCR, rolling circle amplification and nucleotide sequence analysis, the causal agent was identified as Mungbean yellow mosaic India virus (MYMIV). This is thought to be the first report of MYMIV infecting cucumber in Oman. Cucurbits in Oman are affected by another bipartite begomovirus, Watermelon chlorotic stunt virus, and MYMIV has been reported to infect other important horticulture crops in Oman.