Geriatric nursing activities are closely related to patient safety; therefore, nurses’ efforts to improve patient safety in geriatric hospitals are important. In the present study, we investigated the relationships between person-centered care practice, patient safety competence, and patient safety during nursing activities in geriatric hospitals. We used the following tools to investigate the factors affecting patient safety during nursing activities: (a) the Korean version of the Person-Centered Care Assessment Tool (P-CAT), (b) the Patient Safety Competence Assessment Tool for Nurses, and (c) the Patient Safety Nursing Activities Assessment Tool for geriatric nurses. The questionnaire survey was completed by 186 geriatric nurses in 12 geriatric hospitals from 1 August to 31 August 2018. We analyzed the survey data using a t-test, one-way ANOVA, Pearson’s correlation coefficient, and multiple regression. We identified patient safety skills (β = 0.417, p < 0.001) and age (β = 0.209, p = 0.035) as key factors that influence patient safety during nursing activities. Therefore, to improve the quality of patient safety during nursing activities conducted by geriatric nurses, it is necessary to develop strategies to improve patient safety skills and expand the pool of competent nurses with clinical experience.