This study developed an end-of-life (EOL) care nursing knowledge scale for Japanese geriatric nurses (ELNKS-JG) to measure nurse knowledge of EOL care for older adults. It also was used to evaluate the quality of The End-of-Life Nursing Education Consortium-Japan Geriatric. Participants were 1168 nurses employed in 32 institutions across Japan. The items of our measure were developed to cover 8 important topics: principles of EOL care for older adults; pain management; symptom management; ethics of care; cultural and spiritual considerations; communication; loss, grief, and bereavement; and caring for final days. The measure included 51 items with an overall Cronbach α coefficient of 0.87 and an intraclass correlation coefficient of 0.81. Our measure, the ELNKS-JG, was confirmed to have good internal consistency, test-retest reliability, content validity, and known-groups validity. This scale's items included knowledge about noncancerous diseases, physical changes due to aging, family care, and multidisciplinary collaboration. The ELNKS-JG comprehensively measures a nurse's knowledge of EOL care for older adults in any EOL setting. Furthermore, this scale can evaluate educational programs aimed at improving care quality and encouraging related activities in facilities that provide EOL care.