In February 2017, ten leaf samples of African basil, commonly known as clove basil (Ocimum gratissimum), showing yellowing mosaic with shortened leaves, and three nonsymptomatic leaf samples, were collected from the experimental fields of the Council of Scientific and Industrial Research-Central Institute of Medicinal and Aromatic Plants in Lucknow, Uttar Pradesh, India. Disease incidence was estimated at approximately 20 to 25%. Based on the results of pathogenicity tests, polymerase chain reaction assays, nucleotide sequence comparison and transmission electron microscopy, the causal agent was identified as Cucumber mosaic virus (CMV) subgroup IB. This is thought to be the first report of CMV subgroup IB naturally infecting African basil in Uttar Pradesh and worldwide. CMV has been reported from many important medicinal and aromatic crops such as Hyoscyamus muticus, Catharanthus roseus, Rauvolfia serpentina and so on, during the past 15 years in India.