To investigate the adaptation process of Generation Z nurses at a tertiary hospital in Korea. This qualitative study using grounded theory. The participants were 17 Generation Z nurses who were working at tertiary hospitals in Korea. Data were collected through in-depth interviews from September 2022 to July 2023. Eight categories and 19 concepts were extracted. The core category was 'accepting deficient myself as a nurse in a vertical culture', which consisted of three phases: chaos, endeavouring to adapt and accepting myself. In the adaptation process at the tertiary hospital, most of the participants felt embarrassed by tasks. The most of them tended to stay away from stressors and endeavour to improve their competence. The participants who had familiarity and a sense of belonging and achievement tended to acknowledge themselves. This study provides help in suggesting the importance of a horizontal organisational culture to Generation Z nurses. Also, the support of senior nurses is needed to encourage Generation Z nurses to accept deficient themselves. Generation Z nurses tended to feel confused by the vertical culture, uncertainty of work and daunting tasks; excessive criticism and rebuke seems to make Generation Z nurses feel a sense of shame. The family-centred culture of nursing organisations could cause conflicts for Generation Z nurses who tend to separate their personal lives from work. Generation Z nurses had no difficulty acquiring knowledge because they had the skills to search for the necessary information, but they experienced difficulty applying this knowledge in practice and becoming familiar with their role as a nurse. We adhered to relevant EQUATOR guidelines of the Consolidated Criteria for Reporting Qualitative Research (COREQ). No patient or public involvement.