ObjectiveThe primary objective was to evaluate the change in the prevalence of daily or occasional tobacco smoking during the first year of the COVID-19 pandemic and to assess if socioeconomic factors were associated with changes in smoking. The secondary objective was to evaluate the association of smoking with adherence to public health measures.MethodsIn this prospective cohort study, using Canadian Longitudinal Study on Aging data (44 139 middle-aged and older-aged adults), the prevalence of smoking during the COVID-19 pandemic (2020) and prepandemic (2011–2018) was estimated using weighted generalised estimating equations. ORs and 95% CIs for the association between smoking and adherence to public health measures (a derived score) were estimated using multinomial logistic regression.ResultsTime (during vs prepandemic) was a significant predictor of smoking (adjusted OR (aOR) 1.12; 95% CI 1.07, 1.17). The adjusted prevalence of smoking during the beginning of the pandemic was 11.2% (95% CI 10.1%, 12.4%), compared with the prepandemic prevalence of 10.1% (95% CI 9.1%, 11.2%), with p<0.001. Factors associated with an increase in smoking were male sex, being aged 55 to 74 years, residing in Ontario or British Columbia, immigrant background, belonging to a racialised group, higher income and being married/common-law relationship. Smoking was associated with increased odds of high adherence to public health measures (aOR 1.53; 95% CI 1.31, 1.78).ConclusionAmong middle-aged and older adults in Canada, there was a small increase in the adjusted prevalence of smoking early in the pandemic. Daily or occasional smoking was associated with greater adherence to public health measures.