This study aims to explain the mechanisms linking structural economic uncertainty, the transition to adulthood, and the transformation of marriage and fertility patterns in contemporary Iran. It argues that reducing demographic shifts solely to cultural changes or individualistic preferences fails to capture the material context of generational decision-making. The theoretical framework integrates Oppenheimer’s career-entry theory, Becker’s economic theory of fertility, and the life-course perspective, emphasizing concepts such as “status anxiety” and “defensive rationality.” The methodology employs an integrative research synthesis and secondary trend analysis, triangulating official statistical data, national surveys, and existing empirical literature. Findings indicate that persistent economic uncertainty—manifested in labor market instability, rampant inflation, and the housing affordability crisis—has eroded the foundations of youth autonomy. This has disrupted the normative sequence of the transition to adulthood, resulting in a state of “suspended adulthood.” Cognitively, this environment triggers “status anxiety” and a shift toward “defensive rationality,” where youth prioritize risk mitigation over utility maximization. Consequently, marriage and childbearing are increasingly perceived as high-cost, high-risk “investments,” leading to adaptive postponement and strategic fertility limitation. The study concludes that contemporary demographic shifts do not reflect a decline in the cultural value of family; rather, they reveal a widening gap between the cultural ideal of family formation and its structural feasibility. Effective population policy requires a fundamental shift from short-term financial incentives to structural economic stabilization, addressing the youth housing crisis, and expanding comprehensive welfare support.