The study aimed to find out to what degree suicidal thoughts and associated factors affect the suicide risk of advanced cancer patients. The frequency of suicidal thoughts among patients with cancer, especially in the advanced stages, is about 3 times greater than the adult average in South Korea. We recruited 457 participants with four types of cancers (colon, breast, cervical, and lung) using stratified sampling. Data collection was carried out through one-on-one interviews by trained nurses using a structured questionnaire. Advanced cancer patients with high, vs. low, levels of anxiety and pain had a higher suicide risk. In contrast, having one’s spouse as the primary care provider was associated with a low suicide risk. Overall, the three factors of anxiety, pain, and the primary caregiver being one’s spouse explained 17.2% of the variance in suicide risk. In conclusion, we derived influencing factors of suicide risk using a sample of patients with various types of advanced cancer. The results provide systematic baseline data for preparing nurse-led interventions to prevent suicidal thoughts and suicide attempts among advanced cancer patients.