Background and aims Little is known about the factors associated with retention in smoking cessation trials, especially for low-socioeconomic status (low-SES) smokers. This study examined the factors associated with retention of low-SES smokers in the Australian Financial Interventions for Smoking Cessation Among Low-Income Smokers (FISCALS) trial. Design A two-group parallel block randomised open-label trial with allocation concealment. Setting Australia. The study was conducted primarily by telephone-based interviews with nicotine replacement therapy delivered via mail. Participants 1047 low-SES smokers interested in quitting smoking were randomised. Measurements Participants completed computer assisted telephone interviews (CATIs) at baseline, 2-month and 8-month follow-up. Smoking-related, substance use, mental or physical health, general psychological constructs, sociodemographic and recruitment sources association with retention at 8-month follow-up were examined using binary logistic regression. Findings 946 participants (90%) completed the 2-month follow-up interview and 880 participants (84%) completed the 8-month follow-up interview. Retention at 8-months was associated with higher motivation to quit (OR: 1.15; 95% CI: 1.04, 1.27 p < 0.01), more recent quit attempts (OR: 1.20; 95% CI: 1.04, 1.40 p < 0.05), increasing age (OR: 1.05; 95% CI: 1.03, 1.07 p < 0.01), and higher level of education (OR: 2.24; 95% CI: 1.45, 3.46 p < 0.01). Lower retention at 8-months occurred for those participants recruited from posters placed in Department of Human Service Centrelink Offices (OR: 0.56; 95% CI: 0.35, 0.89, p < 0.05) compared to participants recruited from Quitline services. No significant differences in retention were found for participants recruited via newspaper advertisements or word of mouth compared to Quitline services. No significant associations were found between health-related or behavioural factors and retention. Conclusions In the context of high overall retention rates from disadvantaged smokers in a randomised trial, retention was greater in those smokers with higher motivation to quit, more recent quit attempts, increased age, higher level of education and for those recruited through Quitline or newspaper advertisements.