Tariff policies serve as a key instrument for protecting domestic industries under economic sanctions. Given Iran's dependence on oil revenues and the intensification of international restrictions, examining the impact of macroeconomic variables and sanctions on the level of tariff protection is of strategic importance. This study aims to investigate the effect of the exchange rate, inflation, and economic sanctions on the effective tariff rate of industrial goods in Iran over the period 1978–2024 (1357–1403). After calculating the effective rate of protection for ten industrial groups using time-varying input–output tables, two equations were estimated as a simultaneous system (three-stage least squares), and the long-run and short-run relationships were analyzed through a vector error correction model. The findings showed that sanctions, with a coefficient of 0.465, had a positive and significant effect on the effective tariff rate, which rose from 0.624 to 1.087 following the intensification of sanctions. The exchange rate (0.309) and inflation (0.512) also exhibited positive and significant relationships. However, although tariff protection preserved output volume, its increase was accompanied by a decline in industrial production growth (56.3%), a fall in export share (27.8%), and reduced productivity, such that the net effect of sanctions on industrial production was estimated to be nearly neutral. The results indicate that tariffs alone do not improve industrial efficiency, and combining them with productivity and competitiveness policies is essential.