Background and Objectives: Limited research has focused on the relationship between cancer, job loss, and factors associated with job loss among older workers. Therefore, in this study, we aimed to examine the relationship between cancer and intention to leave and between physical-health-related issues, mental-health-related issues, and cancer-related symptoms and intention to leave among older workers with cancer. Materials and Methods: This cross-sectional internet-based study included 4498 workers aged 60–75 years. Intention to leave was assessed based on whether individuals considered quitting their current jobs in the near future. Results: A multivariate logistic regression analysis showed a significant association between cancer and intention to leave (adjusted odds ratio [aOR]: 1.42, 95% confidence interval [CI]: 1.01–2.00, p = 0.045). In addition, physical-health-related issues (aOR: 2.33, 95% CI: 1.10–4.92, p = 0.026) and mental-health-related issues (aOR: 4.44, 95% CI: 1.80–10.98, p = 0.001) were significantly associated with the intention to leave. Conclusions: Healthcare providers and employers must address the physical- and mental-health-related issues facing older workers with cancer to help them secure their employment.