Louis J. Ignarro was born in 1941 in Brooklyn, New York. His parents were Italian immigrants and his father was a carpenter in Torre del Greco, near Naples. Ignarro grew up in Long Beach, NY, which is a suburb of New York City, NY on the south shore of Long Island, NY. Ignarro received his first chemistry set as a gift at the age of 8.

Ignarro attended Central Grade School and Long Beach High School. A strong interest in science led Ignarro to Columbia University where he studied chemistry and pharmacology and in 1962 received a bachelor's degree in pharmacy. Ignarro then attended the University of Minnesota where he received a Ph.D. in pharmacology. His university studies also concentrated in chemistry, enzymology and cardiovascular physiology, which resulted in several published papers. While at the University of Minnesota, Ignarro studied under eventual Nobel Prize-winning Chemist Paul Boyer.

Ignarro's work continued at the NIH in the fields he'd studied, collaborating with many other Scientists to discover regulatory mechanisms of the cardiovascular system that would lead to his most famous work. This was his first time to apply his education outside of an academic setting. In 1968, Ignarro left the NIH to work for Geigy Pharmaceuticals. With this company, Ignarro helped develop new drugs and was able to continue research into new areas of pharmacology including cyclic GMP. After Geigy merged with Ciba Pharmaceuticals, Ignarro decided to move back to the world of academia, this time as a professor.

In 1973, Ignarro accepted the position of Assistant Professor of pharmacology at Tulane University School of Medicine in New Orleans, LA. Tulane was chosen partially because it would provide a good environment for continued research into cyclic GMP. While studying cyclic GMP, Ignarro read a paper by Ferid Murad, who demonstrated that nitric oxide elevates cyclic GMP levels. Ignarro then speculated that nitric oxide could be the key to relaxing vascular smooth muscles. In turn, this led to his extensive research on the subject. Ignarro's research demonstrated that nitric oxide serves the functions of vasorelaxant and inhibitor of platelet aggregation, with both effects mediated by cyclic GMP.

Ignarro continued his research at Tulane. In 1984 he realized that the properties of nitric oxide were the same as those seen in the endothelium derived relaxing factor previously-identified by Robert Furchgott 3 years earlier. The exact nature of the EDRF was up to this point unknown. Interestingly, Furchgott and Ignarro came to similar conclusions about nitric oxide as the EDRF around the same time and both presented evidence at conferences during 1986 demonstrating nitric oxide's role as EDRF.

During the decades since Ignarro and Furchgott's initial research, thousands of studies have been published about the effects of nitric oxide as the endothelium derived relaxing factor. This has led to the development of erectile dysfunction drugs such as Viagra and nutritional supplements designed for cardiovascular health and athletic performance. In 1985, Ignarro moved from New Orleans to Los Angeles where he accepted a position at the UCLA School of Medicine and continues to research and teach.

Ignarro has published numerous research articles. He received the Basic Research Prize of the American Heart Association in 1998. This was in recognition of his outstanding contributions to the advancement of cardiovascular science. That same year, he was inducted into the National Academy of Sciences and the following year, into the American Academy of Arts and Sciences. Because nitric oxide is indirectly involved in the action of this drug, he is sometimes referred to as the "Father of Viagra".

While testifying before Congress in 2000, Ignarro remarked: "Only in America could the son of an uneducated carpenter receive the Nobel Prize in Medicine".

In 2003, Ignarro published a study based on ingredients found in Niteworks in the Proceedings of the National Academy of Sciences, where, as a member of the National Academy of Sciences, he can submit papers without review and without disclosing his financial interest to the publication. After Ignarro's ties to Herbalife were revealed, the journal issued a correction to the article, citing Ignarro's undisclosed "conflict of interest." UCLA conducted its own investigation and determined that Ignarro did not act improperly. Ignarro has publicly acknowledged the conflict of interest as a mistake and has continued to publish extensively on the subject of nitric oxide.