BackgroundMalignancy is a critical factor affecting death anxiety and psychological well‐being. This study examined the impact of malignancy on death anxiety and psychological well‐being in middle‐aged and older adult patients undergoing abdominal surgery and projected it along with sociodemographic profiles.MethodsThis study is quasi‐experimental in design. It was conducted with patients undergoing abdominal surgery at a university hospital due to suspected malignancy. A total of 93 patients participated in the study: 57 patients diagnosed with malignancy were included in the experimental group, while 36 patients without a malignancy diagnosis were included in the control group. Data were collected using a questionnaire developed by the researchers based on the literature, the ‘Turkish Death Anxiety Scale’, and the ‘Psychological Well‐being Scale’. The analyses revealed that the data were normally distributed, and parametric tests were used to analyze differences between demographic variables and groups. Cohen's d and r values were examined to assess the effect size in the tests.ResultsThe study found a significant difference in death anxiety between the experimental and control groups (P < 0.05), with higher mean scores in the experimental group. Malignancy had a large effect on death anxiety (d = 1.42). Additionally, the control group had significantly higher mean psychological well‐being scores compared to the experimental group (P < 0.05).ConclusionsThe study found that malignancy significantly affects death anxiety and psychological well‐being. Increased death anxiety in patients with malignancy was associated with reduced psychological well‐being. Thus, assessing death anxiety and providing targeted nursing care are essential for supporting the psychological well‐being of these patients.