Objective: To investigate the impact of psychological treatment based on the Rosental effect on patients undergoing surgery for stomach cancer in terms of their level of hope, anxiety, and depression. Methods: This study included 98 patients with stomach cancer who were admitted to our hospital between May 2020 and February 2022. Patients were selected using a random number table. Each group will have half of the patients as their controls and the other half as their observers. While those in the control group received business as usual care, those in the observation group received Rosenthal effect-based psychological care. It was evaluated how the two groups' mental health changed after the intervention compared to before it. Results: In terms of gender, age, tumour stage, and tumour location, there were no significant differences between the two groups (P > 0.05). Fear of cancer recurrence, dealing with illness, hope level, and negative mood were not significantly different between the two groups before treatment (P>0.05). The intervention significantly improved the medical coping modes questionnaire (MCMQ) score, the Herth hope index (HHI) score, as well as the FCRI score in the intervention group compared to the control group, and the Self-Rating AnxietyScale score in the intervention group compared to the control group. The scores on the Self-Rating Depression Scale (SDS) and the Beck Depression Inventory (BDI) were both substantially (P<0.05) lower in the treatment group than in the control group. Conclusion: Following surgery, psychological treatment based on the Rosenthal effect can increase the level of hope among patients with stomach cancer, control anxiety and depression, and aid in physical recovery.