The main objective of this article is to broaden the knowledge of professional coaches with certain aspects of clinical psychology. The focus is on those symptoms demonstrated by patients, which could be the early warning signs of mental illness or problems when psychiatric or psychological help is necessary. Professional Coaches have a responsibility to distinguish their services from therapy, because they are not legally sanctioned and not allowed to offer therapy. Coaching does not focus on dysfunction, diagnosis, symptoms or the past, and that is the reason, why these topics are not included in the curriculum preparing one for this profession. But an ethical coach should observe when a client needs a therapy instead of, or in addition to, coaching and will recommend accordingly. As well as a good therapist, could observe when a client is ready to take greater responsibility for their own life and recommend coaching. This article will argue the significance and importance of aforesaid awareness and expertise, which will allow professional coaches will be able to recognize whether a client would benefit from coaching or should seek guidance from other specialists. For this reason, in this article the Global Assessment of Functioning (GAF) is presented and discussed, as well as the characteristics behind the concept of psychological diagnosis.