INTRODUCTION: Nigeria is committed to reducing industrial trans-fatty acids (iTFA) from the food supply, but the potential health gains, costs and cost-effectiveness are unknown. METHODS: The effect on ischaemic heart disease (IHD) burden, costs and cost-effectiveness of a mandatory iTFA limit (≤2% of all fats) for foods in Nigeria were estimated using Markov cohort models. Data on demographics, IHD epidemiology and trans-fatty acid intake were derived from the 2019 Global Burden of Disease Study. Avoided IHD events and deaths; health-adjusted life years (HALYs) gained; and healthcare, policy implementation and net costs were estimated over 10 years and the population's lifetime. Incremental cost-effectiveness ratios using net costs and HALYs gained (both discounted at 3%) were used to assess cost-effectiveness. RESULTS: Over the first 10 years, a mandatory iTFA limit (assumed to eliminate iTFA intake) was estimated to prevent 9996 (95% uncertainty interval: 8870 to 11 118) IHD deaths and 66 569 (58 862 to 74 083) IHD events, and to save US$90 million (78 to 102) in healthcare costs. The corresponding lifetime estimates were 259 934 (228 736 to 290 191), 479 308 (95% UI 420 472 to 538 177) and 518 (450 to 587). Policy implementation costs were estimated at US$17 million (11 to 23) over the first 10 years, and US$26 million USD (19 to 33) over the population's lifetime. The intervention was estimated to be cost-saving, and findings were robust across several deterministic sensitivity analyses. CONCLUSION: Our findings support mandating a limit of iTFAs as a cost-saving strategy to reduce the IHD burden in Nigeria.