To understand whether patient-reported experiences with lung cancer may create teachable moments (TM) for their relatives as evidenced by shifts in their risk perceptions, affective response, and self-image and in turn, motivation to quit smoking.Patients at a comprehensive cancer center (n = 152) completed a survey within 6 months of lung cancer diagnosis to assess their cancer-related symptoms and openness and enumerated relatives who were smokers. Relative smokers (n = 218) then completed a survey assessing their risk perceptions, affective response, and self-image as a smoker related to the patient's diagnosis (TM mechanisms), and their motivation to quit smoking. Cross-sectional mediation and moderation analyses were conducted to explore the links between patient-reported experiences, and relatives' TM mechanisms, and motivation to quit smoking.Relative-reported affect was a significant mediator of the association between patient-reported symptoms and relative smoker's desire to quit. Relatives' self-image was a significant moderator of the association between patient-reported symptoms and relative smoker's desire to quit, such that patients' reported symptoms were associated with relatives' desire to quit only when the relative smoker reported a generally positive self-image as a smoker. No evidence was found for moderated mediation. However, the link between symptoms and negative affect was moderated by perceptions of risk.Whether smokers experience a family member's lung cancer as a TM is influenced by multiple interrelated cognitive and affective factors that warrant further exploration. Clearer understanding of these factors could inform how to re-invigorate and sustain this motivation to promote concrete actions toward smoking cessation. Copyright © 2015 John Wiley & Sons, Ltd.