Marriage with teenage girls is an important health and social challenge, which is caused by various factors. Considering that no research has been done to show the reasons for men’s desire to marry teenage girls, this research was conducted with the aim of identifying the reasons why men marry teenage girls in western Iran. This qualitative research was conducted with the conventional content analysis approach among 37 men in western Iran who married to girls under the age of 18. Targeted, theoretical, and snowball sampling methods were used to reach the participants. To collect data, semi-structured interviews were used both in-person (20 people) and online (17 people). Data analysis was done with Graneheim and Lundman approach and checking the accuracy and strength of the results with Guba and Lincoln criteria. One core category, 9 subcategories, and 88 initial codes were obtained from the data analysis. The core category, foresight along with desired upbringing, included the subcategories of getting sure of purity, to bring up the girl, seeking sexual pleasure, dominating the wife, low expectations, appropriate fertility, encouragement of social organizations and families, following models, and cultural beliefs. The reasons for men marrying teenage girls are rooted in personality traits, family encouragement, and the cultural and social context of the society. Marriage with teenage girls can be prevented by intervening at different levels and taking measures such as training and raising men’s awareness about the consequences of marrying teenage girls, changing men’s cultural and gender beliefs, raising the awareness of parents and social organizations about the adverse effects of child marriage, and establishing appropriate laws.