Purpose: This study was done to examine actor and partner effect of dementia knowledge, self-efficacy and depression on dementia preventive behavior in elderly couples. Methods: Participants were 115 couples aged 60 years or over who met eligibility criteria. All measures were self-administered. Data were analyzed using SPSS 18.0 and AMOS 18.0 program. Results: Dementia knowledge in elderly couples showed actor and partner effect on dementia preventive behavior. Self-efficacy in the wife did not have direct effects on dementia preventive behavior, but showed indirect effects through dementia knowledge. Self-efficacy in the husband showed direct effects on dementia preventive behavior and indirect effects through dementia knowledge. Wife"s depression had direct actor effect on dementia preventive behavior and indirect effect through self-efficacy and dementia knowledge. Husband’s depression did not have direct actor effect on dementia preventive behavior, but indirect effect through self-efficacy and dementia knowledge. Effect size of wives’ dementia knowledge, self-efficacy and depression on dementia preventive behavior was larger than that of husbands’. Dementia preventive behavior, dementia knowledge and depression had a mutual effect. Conclusion: Results indicate that to promote dementia preventive activity in elderly couples, programs should be conducted for both of the couple, but focused differently for wife and husband.