: A growing body of empirical evidence suggests that psychotherapy is more effective when therapists tailor interventions to fit their specific clients' needs, a concept referred to as therapist responsiveness in the psychotherapy literature. However, the question of how therapists learn to become responsive rarely has been examined. : The central question of this study, put to eleven graduate student therapist trainees, was, "How did you learn to be responsive to clients as a novice therapist, and in what ways have you become responsive?" A critical-constructivist grounded theory method was employed to generate themes from trainees' replies. : The analysis showed that trainees learned to improve their responsiveness to clients by: (1) becoming more aware of cues that signaled the need to adapt interventions (as related to psychotherapy change processes, client-therapist relational dynamics, clients' identities and cultural contexts, and the maximizing of clients' agency); (2) developing attunement to their own emotions and engaging in self-care; and (3) adopting mindsets that facilitated their trying new relational or therapy approaches while also maintaining professionalism. Based upon these findings, preliminary suggestions for responsiveness training are presented to guide programs that wish to train responsive psychotherapists .