Annona muricata L. commonly known as soursop is an underutilized fruit crop species in Sri Lanka gaining much importance in the recent past due to its high nutritional and medicinal value. Soursop germplasm collections are available within the country and assessing the genetic diversity is needed to proceed with conservation, detecting promising lines and breeding programs. This study was conducted to assess the genetic diversity of 50 soursop individuals using Inter-Simple Sequence Repeat (ISSR) markers. The study was conducted at Plant Genetic Resources Centre of the Department of Agriculture in Gannoruwa during 2017 to 2019. DNA of the 50 soursop samples were extracted using CTAB method and Polymerase Chain Reaction (PCR) was carried using 13 Inter Simple Sequence Repeat (ISSR) Markers. PCR products were visualized using 1.5 percent Agarose gel electrophoresis under the Biorad Gel documentation system and analyzed using POPGENE 1.31. PCR amplified 139 bands from 13 ISSR markers among which 118 were found to be polymorphic. The polymorphic band percentage was 85 percent while as the average number of bands observed (Na) was 1.8489 and the effective allele number (Ne) was 1.5377. The Nei's gene diversity index (h) was 0.3079. The Shannon Information Index (I) found to be 0.4556. Dendrogram constructed based on the UPGMA method clustered the studied accessions into four major clusters at 80 percent similarity level. Results revealed considerable degree of genetic diversity existed within the studied soursop germplasms at Sri Lanka. Existing genetic diversity within soursop individuals will serve as germplasm bank to identify and utilize potential germplasm resources for conservation and future breeding programs to develop quality soursop varieties in Sri Lanka.