The purpose of this study is to examine the effects of defense mechanism parameters in the relationship of unstable early object relations and relationship addiction. For this purpose, the data were collected by 323 young adult lived in Seoul and Gyeong–sang Province. This study used the BORI, K–DSQ, RAQ as measurement tools. The data were analyzed by SPSS 21.0 and SPSS Macro. The results of this study are as follows. First, there was a significant correlation between unstable early object relations and relationship addiction. Second, the projection defense mechanism played a role as a mediation effect between early object relations and relationship addiction. This study examined both the effect of unstable early object relations on relationship addiction and the role of defense mechanism between the unstable early object relations and addiction relationships. These results suggest that it is important to understand clients’ defense mechanism formed by their early object relations in order to effectively deal with relationship addiction. Finally, it covered the limitations of this study, and presented implications for Christian counseling and further studies.