This study explores the impact of the psychosocial development and attachment styles of individuals on subsequent partner selection and marital satisfaction among Korean couples. A sample of 100 co-habiting Korean married couples (N=200) and 100 couples planning to marry (N=200) were collected via convenience sampling, and this research focuses on heterosexual couples. Data were assessed using four psychological measures consisting of 162 questions, which solicited socio-demographic data, the degree of unfulfilled psychosocial tasks and psychosocial resources, the attachment styles and the quality of the couple's relationship. The data was analyzed using descriptive statistics: Chi-square, t-test, Mann-Whitney U test, ANOVA, and a Tukey post hoc analysis. The findings indicate that similarities exist between partners in partner selection in both married and planning to marry couples in their psychosocial development and attachment styles.