Dialectical behavior therapy (DBT) can be considered the most effective treatment when attending to problem behaviors that define borderline personality disorder (BPD). This therapy employs chain analysis as the tool for accounting for contextual variables that maintain these behaviors. However, these detected variables are descriptive and temporal rather than strictly functional. That is, the role of contextual variables is analyzed regarding temporal relations with the problem behavior, but not in terms of contingency relations that allow showing their function. Thus, a functional approach to hypothesize these contingency relations between responses and the variables that control them was carried out. Behavior functional analysis was employed as a tool and functional hypotheses of the DSM-5-TR criteria for BPD were conducted. The conclusion is that the proposed approach can be used as a guide to elaborate functional hypotheses about cases displaying the behaviors defined in the diagnosis.