Objectives To explore the anxiety, depression, stress and related factors in the primary caregivers of inpatients with cancer. Methods A total of 235 selected caregivers of inpatients with cancer were included as the research subjects, and the Depression-Anxiety-Stress Self-Rating Scale 21 (DASS-21) was used to evaluate their depression, anxiety and stress. The data were statistically analyzed using SPSS 25.0 software. Results The study showed that the caregivers of cancer patients had different levels of depression, anxiety and stress, but all rates were above the normal range, with 51.7％, 56.0％ and 34.9％ of subjects respectively reporting these conditions. In addition, the above indicators were correlated with the caregivers' gender, age, relationship with the cancer patients, the family's economic status, religious belief and duration of caregiving: being female (T-Statistic =-2.061, P = 0.040) and having a low income (F = 2.627, P = 0.035) were positively correlated with the caregivers' stress level. Having a low income (F = 2.804, P = 0.027) was also positively correlated with the depression scores. When the caregivers were the patient's parents, they had higher levels of anxiety (F = 2.429, P = 0.036) than caregivers in other relationships. The results of a linear correlation analysis showed that the depression of caregivers was negatively correlated with the family's economic status (r value =-0.244, P < 0.01) and positively correlated with the duration of caregiving (r = 0.138, P < 0.05). The anxiety score was positively correlated with the caregivers' age (r = 0.141, P < 0.05) and duration of caregiving (R = 0.132, P < 0.05), but negatively correlated with the family's economic status (r =-0.187, P < 0.01). The stress level was positively correlated with the caregivers' gender (r = 0.137, P < 0.05), age (r = 0.210, P < 0.01), duration of caregiving (r = 0.171, P < 0.01) and current job status (r = 0.165, P < 0.05), but negatively correlated with the family's economic status (r =-0.202, P < 0.01). The results of a multiple stepwise regression showed that age and religious belief were significant predictors of stress, while the family's economic status was a significant predictor of depression, and age was a significant predictor of anxiety. Conclusion The caregivers of hospitalized cancer patients showed varying degrees of anxiety, depression and stress, according the psychological assessments; the provision or interventions might be helpful for these individuals.