Background: Diarrhea is a prevalent health issues in developing countries, and often linked to soil-transmitted helminthiasis (STH). This study aims to investigate the association between STH and diarrhea in Perobatang, Southwest Sumba (SBD). Method: A cross-sectional study was conducted in Perobatang, SBD, in January 2017. Participants were children aged 1 – 15 years. Stool samples were collected from each child and examined macroscopically for signs of diarrhea and microscopically for STH eggs. Positive cases were treated with albendazole. Result: A total of 333 samples were analyzed and 257 children were infected with STH (77%). The prevalence of A. lumbricoides was 56%, T. trichiura was 55%, and hookworm was 5%. Mixed infections were more common in children 6 – 15 years. Ninety-two children (28%) exhibited diarrhea. A significant association was observed between the STH infection (combination of all three worm species) and diarrhea incidence (chi-square test, p < 0.05). However, no correlation was found between the prevalence of single infections or the combination of two worm species and diarrhea incidence. Conclusion: STH infections are associated with incidence of diarrhea in Perobatang, Sumba Barat Daya. This finding highlights the necessity for targeted, community-based interventions by local stakeholders to effectively address and mitigate this public health challenge.