Introduction: The aim of this study was to predict marital adjustment among young couples in Ahvaz based on personality traits, differentiation of self and psychological hardiness. Method: Design of this study was descriptivecorrelational. Statistical population included all young couples in the age range of 20 to 40 years old in Ahvaz city in 2019. Participants were 368 male and female that were selected by a multistage cluster sampling method among all young couples. Tools were Neo Five Factor Inventory, Differentiation of self-Inventory, Kobasa Hardiness Questionnaire and Graham– Bisspicrrier Marital Adjustment Questionnaire. Data were analyzed using Pearson’ s Correlation and Multiple Regression Analysis. Results: From Neo personality traits: E (0/75), C (0/49), A(0/48), O(0/33) and N(-0/54); from differentiation of self dimensions: I position (0/56), emotional reactivity (0/40), emotional fusion (-0/19) and from hardiness: commitment (0/41), challenge (0/42) and control (0/42) were related with marital adjustment. Regression analysis showed significantly Beta coefficients for E(0/63), N(-0/11), O(0/07), for I position (0/59), emotional reactivity0/27, emotional fusion (0/26), emotional cutoff (-0/13), and for control (0/26), challenge(0/22) and commitment (0/18). Conclusion: It could be concluded that couples who are higher in E, C, A, O and lower in N, and are more differentiated of self and psychological hardiness are more compatible in their marital life.