[4] In 1969, Jenkins joined Actors Theatre of Louisville under the leadership of Jon Jory, where he served as a company member for three years.
Jenkins appeared on episodes of Homefront, The X-Files, Babylon 5, Star Trek: The Next Generation, Wiseguy, Early Edition, and Beverly Hills, 90210, and starred in Scrubs in the first eight seasons as a main cast member and guest-starred in the ninth and final season.
Jenkins has appeared in many films throughout his career, including The Wizard of Loneliness, Executive Decision, The Abyss, Air America, Last Man Standing, Fled, Gone in 60 Seconds, I Am Sam, The Sum of All Fears, Matewan, Courage Under Fire, and the 1998 remake of Psycho.
He appeared as Fran Goldsmith's father in Stephen King's TV miniseries, The Stand.
Jenkins also had a recurring role on Cougar Town, as Jules' (Courteney Cox) father.