This paper presents the figure, biography and heritage of Jay Haley (1923 - 2007). He was one of the pioneers of family therapy. He worked for many years with other leading pioneers such as M. H. Erickson, N. Ackerman, G. Bateson, V. Satir, S. Minuchin, P. Watzlawick, forming the foundations of contemporary psychotherapy. Together with Don Jackson and Nathan Ackerman, he founded the first family therapy journal "Family Process". He was the director and co-creator of leading family therapy institutions: The Child Guidance Clinic at the University of Pennsylvania in Philadelphia and The Mental Research Institute (M.R.I) in Palo Alto, CA. Haley was co-Director of The Family Therapy Institute of Washington D.C. He was one of the pioneers to form the basics of strategic therapy: planning the therapy, solution oriented and short-term approach. He worked with unconscious processes that occur in families and their impact on functional or dysfunctional working of the system. He introduced new useful terms to the therapeutic practice: stages of family life, perverse triangle, paradox and double bind. It is especially the double bind that helps understand the ongoing communication difficulties within families. Moreover, Haley defined some basic recommendations for family therapists: the necessity to work in a good cooperating team, permanent access to group supervision, and the necessity to plan and foresee the systemic results of one's own activity.