BackgroundThe COVID-19 pandemic has altered the conditions leading people to smoke. Multiple studies have examined changes in population levels of smoking at the start of the pandemic. However, conclusions remain mixed due to the high proportion of studies with poor methods and short follow-up periods.MethodsThis study used longitudinal data from the UKHLS COVID-19 study to derive smoking trajectories among 4,130 UK adults aged 35-64 across four time points over the first year of the pandemic (2018-19, April 2020, September 2020, and January 2021). Random-effects models were used to examine subject-specific changes across time points.ResultsBetween the pre-pandemic estimate and January 2021, there was a significant decline in smoking from 14.8% to 13.1% (PR = 0.89, 95%CI 0.83-0.95). The number of cigarettes smoked per day among smokers increased in April 2020 (B = 0.5, 95%CI 0.0, 1.0) and September 2020 (B = 1.0, 95%CI 0.4, 1.5), but declined back to pre-pandemic levels in January 2021 (B = 0.3, 95%CI -0.3, 0.8). These changes did not vary by sex, ethnicity, relationship status, education, occupation, or household income.ConclusionAmong UK adults aged 35-64, there has been a slight decrease in smoking which was maintained up to January 2021. Whereas there was an increase in cigarette consumption among smokers at the start of the pandemic, this was no longer observable in January 2021. The findings support the argument that the first year of the pandemic is unlikely to have had a negative effect of most middle-aged adult smokers’ trajectory.