The rotting of Porang tubers due to infection of pathogenic fungi is a problem among farmers that is causing financial loss. This study aimed to analyze the potency of pathogenic fungi that caused rotting of Porang tubers. Total of 9 pathogenic fungal isolates was sub-cultured on potato dextrose agar medium. The pathogenicity was assayed on Porang tubers by Koch Postulate test. It was conducted to select the potential fungi which caused to rot tubers. Pathogenic fungi were inoculated on the fresh tuber, then incubated for 14 days. Tuber samples characters, i.e., texture, colour, ethanol content, and monosaccharide content were observed and measured. Fungi that caused rotting tuber were selected for further analysis. Total of 9 isolates of pathogenic fungi was grouped based on phenotype similarities. Three isolates were selected as the most potential fungi causes tuber rot, that are FR, FL and AL based on its ethanol content of 39.04%; 34.55%; 33.56%, glucose 7.74%; 8.61%; 7.28%, galactose 9.14%; 10.53%; 9.66%, mannose 4. 90%; 6.32%; 5.43%, arabinose 4.47%; 5.38%; 4.54%, rhamnose 2.05%; 2.50%; 2.05%, and xylose 3.00%, 3.5%; 2.99%, respectively. Based on phenotype characteristics, isolate of FR and FL were identified as Fusarium sp. while isolate of AL was Aspergillus sp.