The developmental model Greenspan formulated guides the care and treatment of children and infants with developmental and mental health disorders, and his work has led to the formation of regional councils and networks in most major American cities.

He has been recognized internationally as a foremost authority on mental health and disorders in infants and young children, having received awards from both the American Psychiatric Association and the American Orthopsychiatric Association. In 1981, he received the Ittleson Prize, the American Psychiatric Association's award for child psychiatry research. He also received d the Blanche F. Ittleson award from the American Orthopsychiatric Association for outstanding contributions to American mental health. In 2003, he received the Mary S. Sigourney Award for distinguished contributions to psychoanalysis. He has testified before Congress numerous times on policies affecting children and families.[1]

Since 1975, he has written four monographs and 40 books including The Course of Life: Psychoanalytic Contributions to Understanding Personality Development with G. H. Pollock in 1980, with an update in 1989—90. He has also created two videos including First Feelings, which is an introduction to his orientation into social-emotional development. Both in the popular press and in peer-reviewed articles, he has written about a wide variety of subjects that affect human development.

Greenspan recently orchestrated and edited the writing of the Psychodynamic Diagnostic Manual (PDM), a new manual intended to supplement the Diagnostic and Statistical Manual (DSM) currently used to diagnose psychological disorders.

Greenspan lived in Bethesda, Maryland, with his wife and co-author Nancy Thorndike Greenspan. He died on April 27, 2010, of complications of a stroke.