Background: The "only child" phenomenon can swiftly reduce the fertility rate in Iran, disrupt the age pyramid, and be followed by irreparable social and economic harms. Objectives: The goal of this qualitative study was to understand the reasons behind the tendency toward the only child in the Iranian society. Methods: The conventional content analysis was done following the semi-structured interview. Maximum opportunistic sampling was done. The variables taken into consideration for maximum variation were sex, age, education, and occupation. Results: Overall, 46 interviews were conducted. Most of the participants underscored the role of economic causes as the most effective factor. They emphasized that the rise in costs of living was the main factor behind the employment of both parents, particularly the mother, which subsequently robs her of adequate time and patience for parenting. Conclusions: The most important factors contributing to the lack of tendency toward family fertility were, economic factors, rising marriage age; inadequate support for working mother, and being away from relatives. Thus, if policy makers are bent towards intervening in fertility and neutralizing it, they must make the necessary arrangements to improve the families' economic status.