Harleigh Bradley Trecker was born 11 February 1911, in Calery, Illinois, the son of William Henry and Henrietta Trecker. Trecker attended George Williams College (B.S., 1934) and the University of Chicago (M.S., 1938) before embarking upon a career in social work. From 1938 until 1941, Trecker was an instructor at George Williams College and in 1941; he accepted a position at the University of Southern California. In 1951, Trecker accepted the position of Dean, School of Social Work at the University of Connecticut; a position he retained until 1968. From 1968 until his retirement in 1977, Trecker held the position of Professor of Social Work.

Throughout his career, Trecker was involved in several professional societies including the National Conference on Social Welfare, National Association of Social Workers, and the Council of Social Work Education. He was active in his field as a consultant, institute leader, and lecturer, as well as being a prolific writer. He authored twenty books, some of which were translated into foreign languages. He also wrote numerous journal articles and book reviews. Trecker's research focused on social work administration and boards of community service agencies. Trecker received several awards and distinctions including a citation from the American Association of Social Workers (1951) and a certificate of recognition from the Connecticut Social Welfare Conference (1967).

Harleigh Trecker died in 1986.