Johnsey, the son of Floyd G. Johnsey and the former Bertha Lee Herring, worked in coal mines at Sunlight as a teenager, and lost an eye and a lung to mining accidents. He graduated from Curry High School and served in the U.S. Army during World War II. He completed his bachelor's degree in electrical engineering at Auburn University in 1949 and took a job at the Charleston Naval Yard.
Two years later Johnsey returned to his home state to work for Alabama Power, working on safety improvements for underground and overhead line maintenance. Soon he was made head of Birmingham District electric operations, then assistant manager of electric operations company-wide. In 1964 Johnsey was promoted to executive assistant to the chief operating officer. Over the next year he completed a law degree from the Birmingham School of Law. He rose to the positions of vice president and chief financial officer by the time he was 50 and was involved in the development of the company's Farley Nuclear Plant in Dothan. He also served as a consultant to and director of the Drummond Company.
Johnsey took early retirement from Alabama in 1979. Later that year he was one of seven men indicted on federal charges of racketeering and fraud involving Drummond's attempts to gain information about and influence the Alabama State Legislature and Alabama Power Company, specifically regarding its coal usage. The trial judge ordered an acquittal of many of the charges because all elements of the superseding RICO count had not been established by evidence. Johnsey sought to have the remaining charges against him dismissed on double jeopardy grounds. Ultimately he was not convicted of any crime.
Shortly after retiring, Johnsey purchased the Perry Supply Company. He sold it to Drummond in 1986 but retained the position of president of the division, later also taking over the Jasper Corporation. Until he again retired he also served as Drummond's executive vice president in charge of external affairs.
Johnsey was most known, however, as a political operator. He generously cultivated aspiring politicians with financial aid for college and mentorship. His personal contributions, leveraged with corporate donations he directed, made up the majority of campaign funds collected by the majority in the Alabama State Senate. He commissioned monthly political polls and orchestrated influence through an array of political action committee and business leagues. Among his creations were the Business Alliance for Responsible Development, formed in 2005 to oppose the recommendations of the Upper Cahaba Watershed Study and the operations of the Jefferson County Storm Water Management Authority.
Johnsey died in 2007 and is buried at Jasper's Oak Hill Cemetery. He endowed a scholarship to the Auburn University College of Engineering, and was inducted posthumously into the Alabama Engineering Hall of Fame. After his death, Johnsey's estate sued Drummond for allegedly failing to disclose investments belonging to him.
- "Legislator and 3 Coal Officials Indicted in Alabama; Another Defendant Replies" (November 1, 1979) The New York Times
- Flowers, Steve (September 1, 2004) "Godfather of Alabama politics celebrates 80th birthday." Alexander City Outlook
- "Drummond sued by ex-partner's estate" (October 3, 2008) The Birmingham News
- Whitmire, Kyle (July 9, 2018) "This Alabama corruption trial is haunted." The Birmingham News
- Walter F. Johnsey at engrhof.org