This study examines how behavioral and institutional factors shape tax fraud in Indonesia’s decentralized tax administration, with specific attention to land and building tax collection in 35 cities/regencies of Central Java. Drawing on Fraud Diamond Theory, it analyzes the effects of pressure, opportunity, rationalization, and capability on fraudulent tax behavior and assesses whether integrity mediates these relationships. A quantitative explanatory design was applied using survey data from 175 local government employees and analyzed through Structural Equation Modeling. The measurement and structural models were evaluated through outer loadings, composite reliability, average variance extracted, R², and path coefficients. The results show that all Fraud Diamond dimensions significantly influence perceived fraudulent-behavior risk, with pressure and capability emerging as the strongest predictors. Integrity complementarily mediates the effects of pressure and capability but does not mediate the effects of opportunity and rationalization. The discussion highlights that local tax fraud is not merely a moral problem but is also shaped by workload pressure, institutional loopholes, and individual capacity to exploit weaknesses. The study finds that effective fraud prevention requires stronger internal control, digital supervision, reduced work pressure, ethics-based leadership, and sustained integrity development. Keywords: Fraud Diamond Theory, Integrity, Tax Fraud, Local Governance, Public Finance