Dioscorea esculenta commonly known as the lesser yam is cultivated in Batticaloa district of Sri Lanka a small scale.  Pathogenic fungi reduce the quantity and quality of yam produced. Pathological investigations were carried out to find out the fungal organisms associated with yam rot of lesser yam. Eight pieces (2 mm in diameter) of the infected yam tissues were picked from the point of advancement of rot and inoculated on a solidified Potato Dextrose Agar (PDA) medium. Two replicates were made for each of the 4 yam tuber samples and the 8 plates were inoculated. The inoculated plates were incubated at room temperature (30°C) and observations were made daily for possible fungal growth. Sub-culturing was done to obtain pure cultures of the isolates. Cultural characteristics of the fungi were observed and recorded. The identification of the isolates was done by examining the isolates macroscopically and microscopically. The causative fungal pathogen was identified as Fusarium solani (Mart.) Sacc. based on the colony and microscopic characteristics of the pathogen. Fusarium solani produced white cream mycelia.  Macroconidia are three to four-septate, slightly curved, 28-42 x 4-6 µm. Microconidia are abundant, cylindrical to oval, one to two-celled, 8-16 x 2-4.5 µm. Pathogenicity test carried out confirmed this fungal species as the pathological agent of the lesser yam rot. The finding of the causal organism of the yam rot disease would be very useful in choosing effective control measures to extend the life span of yam in storage.