Background: According to the integrated motivational–volitional model of suicide, the perception of defeat and entrapment are the variables involved in the development of suicidal ideation. However, entrapment is not an inevitable consequence of feeling defeated. This transition is moderated by a set of variables relating to the ability to resolve the state of defeat. Aim: We aimed to study the potential moderating role of experiential avoidance in the relationship between defeat and entrapment in young adults. Method: A sample of 644 participants residing in Spain (51.2% female; Mage = 25.91, SDage = 5.14; range = 18–35 years old), selected by sex, age, and education level quotas, completed an online questionnaire consisting of: Defeat Scale; Entrapment Scale; and Acceptance and Action Questionnaire-II; and other sociodemographic variables. Results: Defeat and experiential avoidance had a statistically significant effect on entrapment. The interaction variable (defeat × experiential avoidance) was also statistically significant according to a moderating effect. Limitations: Due to the cross-sectional design, we could not establish causal associations between the variables. Conclusion: People who experience a high degree of defeat and experiential avoidance are more likely to progress to a state of entrapment, being more vulnerable to having suicidal ideation.