Leon J. Yarrow, 60, a psychologist who was an authority on child development and a branch chief in the National Institute of Child Health and Human Development since 1965, died of a heart ailment July 28 at the National Institutes of Health clinical center. He lived in Bethesda.

Dr. Yarrow was a native of Shenandoah, Pa., and a 1941 graduate of the University of Pennsylvania. He earned a doctorate in child development at the University of Iowa in 1946.

He spent three years as a research psychologist with the Child Research Council and was an assistant professor at the University of Colorado's medical school before moving here in 1951. In September of that year, he was named assistant chief of the child development research branch of the old Federal Security Agency's Children's Bureau. He was working for the old Department of Health, Education, and Welfare, when he joined NIH.

Dr. Yarrow was past president of the Society for Research in Child Development, and served on the editorial board of several professional journals, including the "Merrill-Palmer Quarterly of Behavior and Development," and "Infant Behavior and Development."

Survivors include his wife, Marian, of Bethesda; a son, Andrew, of New York City, and his mother, Lillian Yarrow of Frackville, Pa.