Significant shortages of nursing staff threaten the provision of sustainable and high-quality patient care, which may be partially addressed by encouraging experienced staff to postpone their complete exit from the workforce and extend their careers. This qualitative study explored the transition to retirement, the motivation to engage in post-retirement work, and experiences of working after retirement among retired nursing assistants (aged 67-75 years) working in inpatient psychiatric care in Sweden. Interpretative Phenomenological Analysis (IPA) was used and allowed for a detailed, in-depth systematic analysis of data from seven individual interviews. Four superordinate themes were identified: (1) Adjustment difficulties to life as fully retired; (2) Good health as a precondition to work and a consequence of working; (3) The intrinsic joy of working and the importance of feeling competent; and (4) Work and organization-related factors contributed to well-being at work and facilitated an extended working life. Post-retirement work was found to facilitate the transition to retirement and contribute to well-being. Furthermore, good health was considered a prerequisite for, and a consequence of, continued working. Intrinsic motivation to work, being competent in performing the job, along with different work and organizational factors were considered important to continuing working after retirement. The findings contribute to informing the design of work environments and tailored HR strategies that facilitate aging-in-workplace and encourage extended working lives.