This research analyzes the efficiency of the Islamic capital market by applying the methodological framework of multifractal analysis and chaos theory. Focusing on global Islamic stock indices over the period 2010–2023, the present study empirically tests the role of “jurisprudential uncertainty” as an endogenous chaotic factor in these markets, in addition to identifying nonlinear structures. The research methodology is based on multifractal discontinuity analysis (MF-DFA) to estimate the generalized Horst spectrum and identify multifractal behavior, along with calculating the largest Lyapunov exponent to detect chaos. At the same time, a composite index (IFUI) is designed to quantify jurisprudential uncertainty based on changes in Sharia standards, conflicting jurisprudential pronouncements, and news content analysis. The findings show that Islamic indices have a strong multifractal structure (\Delta h between 0.42 and 0.51) and chaotic behavior (\lambda positive and significant), which confirms their weak form inefficiency. The generalized Horst exponent h(2) for all indices is estimated to be significantly greater than 0.5. The results of panel data regression indicate a positive and significant relationship between the Jurisprudential Uncertainty Index (IFUI) and both the multifractality degree (\Delta h) and chaos level (\lambda) variables. Also, the coincidence of the peak of this index with the identified price bubble periods (using the LPPLS model) reveals a possible transmission channel. The main innovation of this research lies in the combination of advanced physical economic methodology with a key theoretical variable unique to the Islamic finance paradigm. The findings, while confirming the inherent complexity and nonlinear dynamics of Islamic markets, emphasize the importance of institutional management of jurisprudential uncertainty through transparency, standardization, and international coordination of Sharia boards to increase the efficiency and stability of these markets.