Recently, researchers from developmental and clinical psychology highlighted epistemic trust (ET) as a key factor for personality disorders. ET is intended as the mental openness to information coming from others during social exchanges. ET develops from signals called ostensive cues, delivered through facial expressions during interactions in a secure attachment context. Similarly, interpersonal trust (IT) refers to the perception of others as not harmful, which is also developed through secure attachment relationships. Our purpose was to suggest a conceptualization of ET as a specific facet of IT. We hypothesize that positive experiences of caregiving promote IT development that includes a specific sense of trust toward others’ knowledge. Moreover, we suggest that the early ability to infer a judgment of trustworthiness from facial cues is the starting point for developing both IT and ET. This conceptualization supports the role of considering both IT and ET in the development of borderline pathology.