Background <p>Despite the common belief that every human being pursues happiness, current evidence challenges this belief with the concept of fear of happiness. Growing literature has examined the relationship between adverse childhood experiences and fear of happiness, but has not yet provided sufficient evidence on how this relationship occurs. Therefore, the present study aimed to address this gap in the literature by examining the mediating roles of self-concept clarity and executive function deficits in the relationship between childhood psychological maltreatment (CPM) and fear of happiness.</p> Methods <p>The participant group consisted of 359 Turkish adults (52.1% males), aged 18 and 62 years (<i>M</i> = 30.24; <i>SD</i> = 8.4). To examine the mediating roles of self-concept clarity and executive function deficits in the relationship between CPM and fear of happiness, a multiple mediation analysis was conducted via the PROCESS macro (Model 4).</p> Results <p>The results revealed that CPM was positively related to fear of happiness and executive function deficits, and negatively related to self-concept clarity. Similarly, a negative correlation between self-concept clarity and fear of happiness was observed, whereas a positive correlation between executive function deficits and fear of happiness was revealed. More importantly, the results indicated indirect associations between CPM and fear of happiness through self-concept clarity and executive function deficits.</p> Conclusions <p>By highlighting both the positive relationship between CPM and fear of happiness and the significant roles of self-concept clarity and executive function deficits in this relationship, these findings contributed to the growing literature on the concept of fear of happiness. Thus, the present study may shed light on practitioners who aim to focus on the psychological outcomes related to adverse childhood experiences in adulthood.</p>