During an interaction, partners adapt their behaviors to each other. Adaptation can have several functions such as being a sign of engagement and enhancing human users’ interaction experience. It is important that virtual agents acting as interaction partners should continuously adapt their behaviors to those of their interlocutors in real time. This paper focuses on creating an interactive virtual agent that is capable of rendering real-time adaptive behaviors in response to its human interlocutor. It ensures the two aspects: generating real-time adaptive behavior and managing natural dialogue. We propose a system of an adaptive virtual agent and choose the e-health application of Cognitive Behavioral Therapy (CBT), which is a mental health treatment that restructures automatic thoughts into balanced thoughts, as a proof-of-concept to showcase the benefit of endowing behavior adaptation to the agent. The virtual agent adapts to the user via the display of nonverbal behaviors, which are generated via a deep learning model, throughout the whole interaction while acting as a therapist helping human users to detect their negative automatic thoughts.