BackgroundRecent studies suggest that state policy, such as cigarette tax policy, is associated with variation in the educational gradient in mortality. However, it is unknown whether state cigarette taxes moderate the educational gradient in mortality directly by incentivizing smoking cessation. MethodsThis study uses 20 years of survey data from the Panel Study of Income Dynamics (N = 89,127 person-years; 751 deaths) merged with administrative data to examine the potential for a single state policy, cigarette taxes, to moderate the education-mortality association through influence on smoking cessation. ResultsIn mortality analyses, higher cigarette taxes are associated with a weaker educational gradient in mortality among smokers and overall. Smoking cessation analyses show higher state cigarette taxes increase the odds of quitting only for low-educated smokers, such that each $1 increase in taxes results in an additional 0.4 to 1 life years for low-educated smokers. For more educated subgroups, the association between state cigarette taxes and smoking cessation is confounded by broader temporal trends. DiscussionState cigarette taxes have potential to weaken the educational gradient in mortality by attenuating educational disparities in smoking cessation, however their direct effect is only on low-educated smokers. The findings help demonstrate how fundamental cause associations are contingent on state policy and vary over time.