["Addiction, EarlyView. ", "\nAbstract\n\nBackground and aims\nResearch indicates that experiencing discrimination may be associated with a return to smoking following a quit attempt. The current study aimed to characterize day‐to‐day relations between discrimination and smoking in the context of a smoking cessation trial for adults with socio‐economic disadvantage.\n\n\nDesign\nSecondary analysis of data from a randomized controlled trial, which used a parallel 2‐group design (unblinded). Eligible participants (adults with socio‐economic disadvantage) were randomly assigned to usual care (UC) for smoking cessation (counseling and pharmacotherapy) or UC plus financial incentives contingent on biochemically verified abstinence. All participants were asked to complete daily smartphone assessments over the first 28 days following a scheduled quit attempt.\n\n\nSetting\nThe smoking cessation trial (parent study) was conducted in a tobacco treatment clinic between 2017 and 2022 in Oklahoma City, Oklahoma, USA.\n\n\nParticipants\nParticipants (n = 256) were primarily female (64.8%) and 40.6% were racially/ethnically minoritized. The average age was 48.97 [standard deviation (SD) = 11.61] years. The average cigarettes smoked per day before quitting was 19.00 (SD = 10.51).\n\n\nMeasurements\nSmartphone assessments measured discrimination [“Do you believe you experienced discrimination yesterday?” (yes/no)] and self‐reported daily smoking [“How many cigarettes did you smoke yesterday?” (smoking [≥one puff]/abstinent)]. Biochemically verified past 7‐day smoking status was assessed at the 4, 8, 12 and 26 week post‐quit follow‐ups. Generalized linear mixed models analyzed the relations between (1) same‐day and next‐day discrimination and abstinence and (2) reporting any discrimination during the smartphone assessment period (SAP) and biochemically verified abstinence at follow‐ups.\n\n\nFindings\nOverall, 62 participants (22.4%) reported 212 instances of discrimination over the SAP. Discrimination was statistically significantly associated with lower odds of same‐day [β = 0.48, 95% confidence interval (CI) = 0.25–0.94] and next‐day (β = 0.47, 95% CI = 0.25–0.86) abstinence, and any discrimination during the SAP was statistically significantly associated with lower odds of abstinence across follow‐ups (β = 0.08, 95% CI = 0.02–0.30).\n\n\nConclusions\nExperience of discrimination appears to adversely impact smoking cessation among adults with socio‐economic disadvantage who are trying to quit smoking and warrants attention in cessation interventions.\nTrial Registration: The parent trial was registered at ClinicalTrials.gov (NCT02737566). The secondary analyses described in this manuscript were not pre‐registered.\n\n"]