Aims: Individuals may return to paid work following retirement, a phenomenon described as “unretirement”. By following recent retirees over time in Germany, Russia and the United Kingdom, we examined whether unretirement is more common for people who are facing financial hardship. Methods: Data are drawn from four prospective surveys: the German SocioEconomic Panel Study (1991–2013), the Russian Longitudinal Monitoring Survey (1994–2013) and, for the United Kingdom, the British Household Panel Survey (1991–2008) and Understanding Society (2010–2014), harmonized ex post. Unretirement behaviour was examined using Cox regression in relation to demographic covariates, as well as education, health and financial adequacy. Findings: The cumulative hazard of unretirement attained around 17% among German participants, 26% among British participants and 42% among Russian participants after 20 years of follow-up. Males, younger and more educated retirees, in better health and with higher incomes were generally more likely to return to work. Participants who were more concerned about their finances were not more likely to unretire in Russia or the United Kingdom and were only more likely to return to work in Germany following adjustment for the other covariates. Conclusions: Unretirement was common, confirming previous largely North American studies depicting retirement as a fluid and flexible process. These results suggest that retired people represent a substantial pool of potential labour, but there was little indication that those most in need were unretiring, particularly in Russia and the UK. This suggests that encouraging greater reliance on employment in later life may cause hardship among older people unable to find suitable work and potentially exacerbate social inequalities.