INTRODUCTION: The total number of cancer-related deaths and new cancer cases in 2020 was 19.3 billion and 10.8 billion, respectively. Therefore, prevention, diagnosis, and treatment of neoplastic disease, as well as management of comorbidities, are of paramount importance. In this regards, poor nutritional status and mental disorders are comorbidity conditions frequently observed in cancer patients. The aim of this study was to assess the association between malnutrition and anxiety in hospitalized adult cancer patients. METHODS: This is a retrospective study. Nutrition Risk Screening (NRS) 2002, body mass index (BMI), daily calorie intake, and weight difference between admission and discharge were used to evaluate nutritional status. Anxiety was assessed with the Hospital Anxiety and Depression Scale (HADS-A). Ordered logistic and linear logistic regressions adjusted for sex and age were used to estimate the association between malnutrition and anxiety in cancer patients. RESULTS: A total of 90 patients were included. Higher NRS risk [aβ = 0.85; 95% CI (0.28-1.42); p = 0.004], disease stage [aβ = 0.77; 95% CI (0.08-1.47); p = 0.029], and cachexia [aβ = 2.20; 95% CI (0.75-3.65); p = 0.003] were significantly associated with anxiety symptoms. Moreover, cancer site different than gastrointestinal cancers was associated with a lower risk of anxiety symptoms [aβ =  - 2.11; 95% CI (- 3.55/ - 0.66); p = 0.005]. CONCLUSION: In the current study, we found a relatively high rate of malnourished patients, indicating the importance of routinely assessing nutritional status and screening cancer patients for mental health issues. This approach could help physicians to treat both in a timely manner, thereby significantly reducing the burden of the disease and improving the quality of life of patients.