In this study, psychometric properties of a Korean-adapted version of the Experiences in Close Relationships—Revised scale were investigated using confirmatory factor analysis (CFA) in conjunction with item response theory. In CFA, neither the supposed two-factor model of Anxiety and Avoidance nor two single-factor models for each factor showed a reasonable fit. In addition, the results from the CFA suggested that the negative-worded and positive-worded items form distinct factors. In the item response theory analysis, the item response matrices of the Korean version did not meet unidimensionality and local independence assumptions. The hierarchical nature of the multidimensionality in the data and residual association among items were dealt with by using a bifactor model. Subsequent exploratory bifactor analysis and full-information item bifactor analysis of graded response data provided support for the bifactor structure of the data and other unique features of the Korean version. The differences between the Experiences in Close Relationships—Revised and the Korean version and their probable causes and implications are discussed.