His father was Moreno Nissim Levy, a Sephardi Jewish merchant born in 1856 in Plevna in the Ottoman Empire (today Pleven, Bulgaria).

Jacob's grandfather Buchis had moved to Plevna from Constantinople, where his ancestors had settled after they left Spain in 1492.

Jacob Moreno's mother, Paulina Iancu or Wolf, was also a Sephardi Jew, born in 1873, and originated from Călăraşi, Romania.

He had rejected Freudian theory while still a medical student, and became interested in the potential of group settings for therapeutic practice.

The marriage ended in divorce, and in 1938 he married Florence Bridge, with whom he had one child, Regina Moreno (born 1939).

It was "an opportunity to get into action instead of just talking, to take the role of the important people in our lives to understand them better, to confront them imaginatively in the safety of the therapeutic theater, and most of all to become more creative and spontaneous human beings.

In his autobiography he wrote "only in New York, the melting pot of the nations, the vast metropolis, with all its freedom from all preconceived notions, could I be free to pursue sociometric group research in the grand style I had envisioned".

[6] The New York Times wrote "He found that acceptance of his theories was slow, particularly because some colleagues deplored his showmanship.

[17] His wife, Zerka Moreno, wrote: "While it is true that Buber broadened the idea of the Encounter, he did not create the instruments for it to occur."

Moreno "produced the various instruments we now use for facilitating the human encounter, sociometry, group psychotherapy, psychodrama, and sociodrama".

In this book, he introduced a famous explanation, why a pandemic of runaways emerged at the New York Training School for Girls in Hudson.