Objective: To explore in depth the psychological perceptions and meaning construction of older adult patients with diabetes during the dietary management process, and to provide a theoretical reference for developing individualized clinical nursing care. Methods: A purposive sampling method was used to select 13 older adult patients with diabetes for semi-structured in-depth interviews. The interview data were collated and analyzed using Van Manen’s analysis method. Results: The psychological experience of dietary management in older adult patients with diabetes included four core themes: (1) Information fog and cognitive shock at initial diagnosis; (2) Self-struggle during the habit reshaping stage; (3) Alternating cycle of hope and frustration in long-term management; (4) Reconstructing normality and searching for meaning in life. Conclusion: Dietary management is an important process for older adult patients with diabetes to reconstruct the meaning of life. Clinical nursing should focus on patients’ psychological experiences and value needs, providing more humanistic and individualized support.