Article Information A rot disease was observed on onion bulbs in major growing areas of Kadapa and Kurnool districts of Andhra Pradesh, India during 2010 to 2012. Based on pathogenicity, morphology and ribosomal DNA spacer sequences, the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg. The fungus was isolated from onion bulbs presenting purple and reddish lesions, obtaining F. proliferatum consistently. The fungus produced effuse white colonies, branched hyphae, short conidiophores, slightly curved macroconidia, and single celled microconidia measuring 5.6-10.5 X 2.0-3.5 μm in diameter. Morphological identification of the fungus was confirmed using ribosomal DNA sequence data. Kotch's postulates were confirmed by performing pathogenicity test on healthy onion bulbs. This is the first report of F. proliferatum causing rot disease on onion bulbs in India; although it had already been reported for onion in the USA and Serbia.