This study assessed the knowledge and attitude toward palliative care for the elderly among health professionals in a tertiary geriatric hospital in Vietnam and explored their determinants. Cross-sectional data were obtained on 161 geriatric health professionals at the National Geriatric Hospital. Modified-Palliative Care Knowledge Test and Frommelt Attitudes Toward Care of the Dying instruments were used to measure knowledge and attitude toward geriatric palliative care. As a result, 40.5% physicians and 74.2% nurses showed insufficient knowledge about geriatric palliative care (p < 0.05). The lowest score was for dyspnea, following by gastrointestinal and pain problems. No significant difference was found regarding the attitude between physicians and nurses (p > 0.05). Health professional category, age, and years of experience were found to be associated with knowledge about palliative care. Meanwhile, only knowledge score had correlations with total attitude score (Coef. = 0.2; 95%CI = 0.1–0.3), attitude toward patients (Coef. = 0.1; 95%CI = 0.0–0.1) and toward patients’ family (Coef. = 0.1; 95%CI = 0.0–0.1). This study highlights a significant knowledge gap and preferable attitude toward palliative care for the elderly among physicians and nurses in the geriatric hospital. Intensive training about geriatric palliative care, focusing on pain, dyspnea and gastrointestinal issue management, should be performed to ensure the quality of palliative care services, especially in nurses.