Working mothers face challenges in pursuing their career aspirations due to work–family conflict. The recent COVID-19 pandemic has posed added challenges for working mothers by increasing care demands while also causing numerous health, economic and social disruptions. In this paper, we examine the impact of COVID-19 on Korean working mothers’ career aspirations. We employ a longitudinal qualitative design by analysing 64 in-depth interviews with 32 mothers of young children in South Korea. By interviewing the same women before (2019) and during the COVID-19 pandemic (2020), we are able to document how working mothers’ career aspirations were impacted by COVID-19. Findings show that all working mothers in the sample experienced increased care demands due to COVID-19. However, the influence of COVID-19 on working mothers’ career aspirations hinged on gendered beliefs related to childcare responsibility. When working mothers believed or were subjected to beliefs that mothers should be the primary caregiver for children (gendered care belief), their career aspirations were tempered or relinquished. On the other hand, those who believed that mothers should not be held solely responsible for childcare (gender egalitarian care belief) continued to pursue their career aspirations or experienced career advancements during COVID-19. Findings suggest that beliefs related to care responsibilities play an important role in working mothers’ pursuit of their career aspirations, and potentially their future careers.