Jannard was born in Los Angeles but was raised in Alhambra, California, the son of a pharmacist, and graduated from Alhambra High School. Jannard was raised in The Church of Jesus Christ of Latter-day Saints. Jannard attended the USC School of Pharmacy but dropped out to travel the southwestern U.S. on a motorcycle. In 1975, he started a one-man Business selling motorcycle parts out of his car at motocross events. He named his company after his dog, Oakley. He began developing his own products: first, custom handlebar grips that conformed to the shape of one's hand and later motorcycle goggles, ski goggles, and sunglasses. One model of sunglasses was used by bicycle racer Greg LeMond, raising Oakley's profile. In the 1980s, he restricted the sale of Oakley sunglasses to the Sunglass Hut (although small specialty shops could continue to sell Oakley sunglasses). In 1991, his company had 200 employees. In 1995, the company went public.
Jannard owns the Fiji islands of Kaibu and Vatu Vara. He also owns a 500-acre island in the San Juan Islands archipelago. In 1999, Jannard purchased two properties in Newport Beach, California, for about $15 million.
In 2005, Jannard started Red Digital Cinema Camera Company. In 2007, Red released the Red One which was used to shoot Wanted, Che, The Informant, and The Girl with the Dragon Tattoo. In 2010, Red released the Red Epic which was used to shoot The Amazing Spiderman, The Hobbit, Prometheus, Pirates of the Caribbean: On Stranger Tides and The Great Gatsby as well as many other feature films.
He sold Oakley in November 2007 for $2.1 billion to Italian company Luxottica, the world's largest eyewear manufacturers and Retailers.
In 2009, Jannard was named one of the 100 Most Creative People by Fast Company Magazine.