The aim of this study is to explore the experiences of music therapist’s musical flow in clinical improvisation. The intervention is clinical improvisation, and in-depth interviews were conducted to eight music therapists who have extensive experience in musical flow. The data was analyzed with consensual qualitative method. There were 6 themes and 23 categories as a result including; ‘factors that promote musical flow’, ‘experiencing the moment of non-musical flow’, ‘musical experience of musical flow’, ‘growth of therapist’s musical flow’, ‘changes of client due to musical flow’, and ‘effort of therapist to enable musical flow’. The result of this study offers in-depth details on how the therapist’s experience of musical flow leads to professional growth of the therapist and changes in the client. It also provides the needs and practical methods to enable musical flow.