Reflective function, a recently introduced concept in the field of individual mental abilities, is defined as the ability to understand the mental states behind one’s own or others’ behaviors, recognizing that these behaviors are expressions of one’s mental states, such as feelings, thoughts, fantasies, beliefs, and desires. Reflective functions allow individuals to understand their mental state and form the basis of self-construction. In academic research, reflective function is often considered an important mediating variable and is used to measure the effectiveness of psychotherapeutic interventions on case outcomes. As an individual’s reflective function is influenced by attachment, early traumatic experiences, parental reflective function, and parental parenting behaviors, primary caregivers play a crucial role in influencing a child’s reflective function. The parenting attitudes of a primary caregiver are apparent patterns of parent-child interaction. An individual’s reflective function impacts self-identity, mental health, and several other aspects. Self-esteem is an individual overall evaluation of self-worth, which can maintain their psychological well-being and may also be influenced by their reflective function. Based on the above, primary caregivers can affect an individual’s reflective function, mental ability development, and individual perception and evaluation of self-esteem. Several studies have confirmed the effect of parenting on self-esteem. However, whether the impact of parenting attitudes on individuals can extend to emerging adulthood, which is the period between 18 and 29 years of age, remains unclear. In addition, no studies have explored the mediating effect of reflective function on parenting attitudes and self-esteem in emerging adulthood. By clarifying the impact of parenting attitudes on individual reflective function and self-esteem, it will be possible to provide counseling or psychotherapy interventions, allowing them to use appropriate therapeutic techniques, such as mentalization-based therapy (MBT). Therefore, this will enable the opportunity to concomitantly improve individual self-esteem and alleviate the negative impact of vulnerable family factors on individuals. Based on the above research motives, the research objectives of this study are as follows:(1) To examine the relationship between parenting attitudes and reflective function in emerging adulthood. (2) To examine the relationship between reflective function and self-esteem in emerging adulthood. (3) To examine the relationship between parenting attitudes and self-esteem in emerging adulthood. (4) To examine the mediating effect of reflective function on parenting attitudes and self-esteem in emerging adulthood. This study employed a questionnaire survey method among emerging adults in Taiwan. A total of 495 valid samples were collected using the Parenting Attitudes Scale, Reflective Function Questionnaire, and Rosenberg Self-Esteem Scale as research tools. The research results are as follows:(1) Caring and autonomy-supportive parenting attitudes have significant positive predictive effects on selfesteem and reflective functions. Overprotective and psychologically controlling parenting attitudes have significant negative predictive effects on self-esteem and reflective function. (2) Reflective function has a significant positive predictive effect on self-esteem. (3) Reflective function has a mediating predictive effect between caring parenting attitudes and self-esteem. The higher the level of caring parenting attitudes, the higher the level of self-esteem that can be achieved through the mediation of a highly reflective function. (4) Reflective function has a mediating predictive effect on overprotective parenting attitudes and self-esteem. The higher the level of overprotective parenting attitudes, the lower the level of self-esteem that can be achieved through the mediation of a low reflective function. (5) Reflective function has a mediating predictive effect on autonomy-supportive parenting attitudes and selfesteem. The higher the level of autonomy-supportive parenting attitudes, the higher the level of selfesteem that can be achieved through the mediation of a high reflective function. (6) Reflective function has a mediating predictive effect between psychologically controlling parenting attitudes and self-esteem. The higher the level of psychologically controlling parenting attitude, the lower the level of self-esteem that can be achieved through the mediation of low reflective functioning. This study contributes to enhancing the attention of clinical practitioners or educators to individual reflective functions. Moreover, it provides different perspectives to examine the effect of parenting of the family of origin on the future development of children and the psychological mechanisms involved.