Purpose: This study was performed to identify the factors influencing the fear of dementia in middle-aged and older adults. Methods: Data on the characteristics, dementia knowledge, dementia attitude, dementia health beliefs, and fear of dementia of 156 participants were collected from January 20 to March 22, 2018, using a structured questionnaire. The data were analyzed with the SPSS/WIN 21.0 program for descriptive statistics, using an independent t-test, one-way analysis of variance, Pearson’s correlation coefficient, and stepwise multiple regression. Results: Significant factors associated with fear of dementia among middle-aged and older adults were subjective life satisfaction (F=3.72, p=.006) and regular exercise (t=6.05, p=.015). Fear of dementia has positive correlations with dementia attitude, perceived susceptibility, perceived severity, and perceived barrier. The determining factors affecting fear of dementia in middle-aged and older adults were perceived severity (β=.46, p<.001), followed by a perceived barrier (β=.20, p=.004) and perceived susceptibility (β=.17, p=.023), and the explanation power was about 47.8%. Conclusion: The results suggest that perceived severity, perceived barrier, and perceived susceptibility be considered in developing the nursing interventions to increase perceived severity, perceived susceptibility, and to decrease perceived barrier to dementia by evaluating dementia health beliefs to manage the fear of dementia among middle-aged and older adults.