Self-disclosure involves revealing information about oneself to others and is critical in relationship formation to develop trust and understanding, leading to emotional intimacy. In psychotherapy, inducing self-disclosure is critical for a therapist to clearly understand clients and suggest relevant solutions. Companion animals have been known to increase human self-disclosure; hence, we hypothesized that virtual animals could have the same effect, which can be strengthened through interaction. To verify this hypothesis, we implemented a mixed-reality-based interaction between humans and virtual cats through Unity. Participants could interact with the virtual cat using hand gestures and voice commands. Psychological states related to self-disclosure were evaluated using questionnaires after the interaction. Furthermore, participants’ responses to the virtual cats were compared with their responses to non-interactive virtual contents. Participants exhibited higher willingness for self-disclosure with virtual cats compared with virtual humans. Interacting with virtual cats was also found to encourage more self-disclosure than interactions with non-interactive states content. Therefore, virtual animals can induce self-disclosure and can be used in psychotherapy. Our findings demonstrate that virtual animals can be used to provide solutions to mental health problems and can be widely applied in the field of psychotherapy.