Economic sanctions have become one of the most decisive external constraints on Iran's economy in the recent decade. However, the intensity and channels through which they affect total factor productivity have not been precisely identified. Adopting a historical-analytical approach, this study examines how sanctions impact Iran's economic productivity and identifies the mediating role of economic sectors. The research utilizes annual time-series data from 2011 to 2022, covering three consecutive phases: intensification of sanctions, partial relief, and severe reimposition. Sanction intensity is measured using a composite index, and its relationship with total productivity and sectoral productivity (oil, industry, agriculture) is analyzed through correlation analysis, univariate and multivariate regression, and trend analysis. The historical approach enables identification of dynamic patterns of economic adaptation across three distinct periods. Findings reveal that sanctions directly explain only 0.3% of total productivity variance. However, 91% of their effect is transmitted indirectly through sectors, with the industrial sector alone accounting for over 90% of total economic productivity variance. During the reimposition period, this sector transitioned from negative to positive averages despite intensified external pressure. The oil sector is the most vulnerable, while agriculture is the most resilient. Trend analysis warns that total economic productivity peaked in 2024 and, without structural transformation, will move toward negative values from 2031 onward. The results emphasize the necessity of focusing policy on enhancing industrial productivity, industrializing agriculture, and transitioning from reactive resilience to structural development.