Hospice cancer caregivers' (HCCs') burden and unmet needs are well documented in the literature through retrospective, standardized self-report surveys. Hospice cancer caregiver daily experiences of burden and unmet needs are rarely captured within a real-time context. The purpose of this secondary data analysis was to characterize HCCs' day-to-day burden and unmet needs with prospective HCC (N = 50) audio diary data between hospice enrollment and patient death. Uncertainty theory provided a framework for analysis. Diaries were transcribed, analyzed deductively and inductively, and organized thematically. Uncertainty in day-to-day experiences was an important driver of HCC burden and unmet needs. Unmet needs included unclear/unmet expectations regarding hospice care team support; not understanding the extent of HCC role and involvement; and communication challenges with hospice team members. Sources of HCCs' burden were dissonance between how they “should” feel and how they actually felt; feeling alone/having no outlet to express feelings; concerns about their own health and subsequent patient impact; and feeling helpless/occupying a liminal space. Uncertainty surrounding HCCs' experiences encompassed interactions with hospice care teams and the nature of end-of-life caregiving with symptom management, the dying process, and the HCC role. Hospice care teams can respond to uncertainty through assessment, understanding, and recognition of the daily context of HCCs.