For terminally ill cancer patients, hope and hopelessness are constructs that significantly impact quality of life. The aim of this study was to examine the relationship between hope and hopelessness in advanced cancer and to identify factors that maintain hope and increase vulnerability to hopelessness. Semistructured interviews were conducted with 22 terminally ill cancer patients. Interview transcripts were analyzed using thematic content analysis to identify patient definitions of these terms and associated cognitions and emotions. Hope and hopelessness were identified as distinct, often co-occurring, and dialectically interacting constructs. The relationship between hope and hopelessness often balanced on acceptance, perceived as diametrically opposed to hopelessness, and conducive to redirecting hope toward new goals. Positive interpersonal relationships enhanced hope, and uncontrolled physical pain increased vulnerability to hopelessness.