Purpose: This study aimed to examine tertiary hospital nurses’ ageism, nursing practice environment and geriatric nursing performance and discover factors influencing geriatric nursing performance. Methods: The research was conducted for 117 nurses working at tertiary hospitals located at Seoul, and data were collected from March 14 to March 31, 2022. The collected data were analyzed with descriptive statistics, t-test, ANOVA, Pearson’s correlation coefficients, and multiple regression using the IBM SPSS 26.0 program. Results: Nursing practice environment was positively correlated with geriatric nursing performance (r=.25, <i>p</i>=.007). The factors influencing geriatric nursing performance were nursing practice environment (β=.25, <i>p</i>=.009) and experience living with the elderly (β=.23, <i>p</i>=.013), and as for the present units, internal medicine (β=.27, <i>p</i>=.009) and integrated nursing·care service (β=.21, <i>p</i>=.042) wards compared with a surgery ward showed an explanatory power of 19.0%. Conclusion: Factors affecting geriatric nursing performance include the current unit where nurses work, nursing practice environment, and experience living with older adults. Based on the research findings, preparing measures for enhancing the quality of geriatric nursing performance is necessary.