One of the variables in a better understanding of career adaptability and optimism levels is family-of-origin experiences. Differentiation of self (DoS) is one of the variables linked to career development. University students with higher DoS maintain an authentic intimacy with significant others while they succeed in individuation. The current study examined the mediator role of self-construal (i.e., interrelational, and self-developmental orientations) on the relationship between the differentiation of self and career adaptability. Our sample was composed of university students; 750 young adults (550 females, 73.3%; 190 males, 25.3%; and ten were missing) participated. The data were gathered from these young adults using the Career Adaptability and Optimism Scale, Differentiation of Self Inventory, Balanced Integrated Differentiation Scale, and Demographic Information Form. Contrary to our hypotheses, findings revealed that self-construal orientations mediated the relationship between differentiation of self and career adaptability in a negative direction. We concluded that a lack of balanced-integrated differentiation (self-construal) complicate the relationship between self-differentiation and career adaptability; we delineated our results considering the literature.