Harriet E. Percy earned a Bachelor of Science degree in biology from McNeese State University, where she was a member of Alpha Upsilon chapter, in 1973. Upon graduation from McNeese, she enrolled in Northwestern State University in Shreveport, Louisiana, where she received a Bachelor of Science degree in nursing in 1976. While working full-time, Harriet attended Tulane University School of Public Health and Tropical Medicine, receiving a master's degree in Public Health/Industrial Hygiene in 1989.
In 1977, Harriet was hired as the first industrial nurse at Uniroyal Chemical Company in Geismar, Louisiana, serving as the only woman responsible for industrial hygiene in the chemical division of the plant. She continued in this role for 15 years until 1992, when she took a position as Administrator-Occupational Health Program at Our Lady of the Lake Regional Medical Center in Baton Rouge. In 1998, she became Corporate Director of Risk Management and Claims Services for The Franciscan Missionaries of Our Lady Health System, the largest healthcare system in Louisiana, a position she still holds today.