ObjectiveTo explore whether expenditure on national tobacco control mass media campaigns moderates the association between motivation to stop smoking and future quit attempts. MethodData were from 2601 people who smoke participating in a population survey with 12-month follow-up between April 2015 and February 2021. We used logistic regression to test associations of (i) baseline level of motivation to stop smoking, (ii) mean monthly tobacco control mass media campaign expenditure in England between baseline and follow-up, and (iii) their interaction, on past-year quit attempts assessed at 12-month follow-up. Covariates included age, sex, occupational social grade, and region. ResultsBetween baseline and follow-up, 38.6% of participants made a quit attempt. Each one-point increase in baseline motivation to stop smoking was associated with 1.37 times greater odds (95%CI = 1.31–1.43) of making a quit attempt over 12-month follow-up. Each one standard deviation increase in tobacco control mass media expenditure between baseline and 12-month follow-up was associated with 13% greater odds of making a quit attempt (95%CI = 1.05–1.23). There was no significant interaction between mass media expenditure and motivation to stop on quit attempts (OR = 1.01, 95%CI = 0.97–1.05); the data provided strong evidence for the null (Bayes factors = 0.07 and 0.04 based on expected effect sizes of OR = 1.5 and OR = 0.67, respectively). ConclusionsAmong people who smoke, self-reported level of motivation to stop strongly predicted whether they made a quit attempt in the subsequent year. Increased expenditure on tobacco control mass media campaigns was associated with increased quit attempts. The association between motivation and quit attempts did not differ according to tobacco control mass media expenditure over this period.