Objective: According to the family systems theory, triangulation is defined as reflecting and conveying the tension between two individuals to a third individual to reduce the existing tension, stress, and anxiety. This study was conducted to adapt the “Triangular Relationship Inventory” to Turkish and to assess psychometric properties. Method: The sample of the study included 337 individuals (234 women and 103 men) aged between 18 and 25 years. The structure validity of the inventory was evaluated with the confirmatory factor analysis and reliability was evaluated with Chronbach's alpha internal consistency coefficient, test–retest method, and item analyses. Results: The result showed that the Turkish form of the Triangular Relationship Inventory showed similar psychometric properties to the original inventory. The structure which consists of the balanced, mediator, cross-generational coalition, and scapegoat subdimensions of 24 items displayed acceptable goodness-of-fit values in the Turkish sample with the 0.91 Cronbach's alpha coefficient while the reliability values of the subdimensions changed between 0.86 and 0.91. Considering the convergent validity of the inventory, there was a negative correlation between the triangular relationship and satisfaction with life and the differentiation of self, and a significant positive correlation with depression, anxiety, and stress. Conclusion: The psychometric properties revealed in this study show that the Turkish form of the Triangular Relationship Inventory is a valid and reliable measurement tool that can be used to measure the triangulation levels and roles of the individuals, who are in the Turkish sample and between the ages of 18 and 25 years, within the family system.