This study employs a qualitative approach with an ethnographic research design aimed at uncovering and describing the mathematical concepts embedded in Jathilan or Jaran Kepang, a traditional Indonesian performing art that represents part of the nation’s intangible cultural heritage. The ethnographic approach enables the researcher to comprehend the meanings, symbols, and mathematical practices that are implicitly expressed within the cultural context of the community of performers. Data were collected through participatory observation, in-depth interviews with artisans, dancers, trainers, and cultural figures, as well as visual documentation and literature review to strengthen field findings. Data analysis was carried out descriptively and qualitatively through the processes of data reduction, presentation, and conclusion drawing within the framework of ethnomathematics. The findings reveal five principal ethnomathematical concepts in Jathilan: (1) planar geometry and symmetry in bamboo weaving patterns, (2) arithmetic sequences in gamelan rhythms and dance movements, (3) proportion and rotation in dancers’ formations, (4) scale and ratio in costume design, and (5) fractal patterns and reflection in the decorative motifs of kuda kepang. This study concludes that Jathilan embodies the intuitive and contextual application of mathematical principles and holds great