Webb was born in Santa Monica, California, on April 2, 1920, son of Samuel Chester Webb and Margaret (nee Smith) Webb. He grew up in the Bunker Hill section of Los Angeles. His father left home before Webb was born, and Webb never knew him. Webb was raised in the Roman Catholic faith of his mother, who was of Irish and Native American descent.

Shortly after leaving his position at Warner Bros., Webb teamed with Universal Television to begin work on a new Dragnet series. A pilot telefilm, based on the Harvey Glatman serial killings, was produced in 1966 for NBC, with Webb's Sgt. Joe Friday joined by Harry Morgan as Officer Bill Gannon. (Webb had tried to get Ben Alexander to reprise his role as Frank Smith, but he was unable to get Alexander to leave the ABC series Felony Squad.)  The new Dragnet premiered as a midseason replacement series on January 12, 1967, and aired until April 16, 1970. To distinguish it from the original series, the year of production was added to the title (Dragnet 1967, Dragnet 1968, etc.). The revival emphasized crime prevention and outreach to the public. Its attempts to address the contemporary youth-drug culture (such as "The LSD Story" episode, guest-starring Michael Burns as Benjamin John "Blue Boy" Carver, voted 85th-best TV episode of all time by TV Guide and TV Land) have led certain episodes on the topic to achieve cult status due to their strained attempts to be "with-it", such as Joe Friday grilling "Blue Boy" by asking him, "You're pretty high and far out, aren't you? What kind of kick are you on, son?" Don Dubbins, who had acted alongside Webb in The D.I. in 1957, was another featured actor in Mark VII Limited programs beginning in the 1960s.  In 1968, Webb and his production partner R.A. Cinader launched Adam-12 on NBC. A spinoff of Dragnet, Adam-12 starred Martin Milner and Kent McCord as a pair of LAPD beat cops, and followed their escapades while on patrol. Running till 1975, for a total of seven seasons, Adam-12 was Webb's second-longest running television series, with the eight seasons recorded by the original Dragnet being the longest.  Also in 1968, Webb and Johnny Carson performed a sketch on The Tonight Show that has since become known as the "Copper Clapper Caper" sketch. Webb, in character as Joe Friday, was working on the case of a robbery at a school-bell factory. Carson played the owner of the factory and victim of the theft, which consisted of each bell being relieved of its clapper (the device that makes the bell ring). The sketch's dialogue consisted of Webb and Carson discussing the situation in deadpan style and using alliteration and tongue twisters to describe the incident, each word having either a "c" or "cl" sound at the beginning. Both Webb and Carson tried desperately not to lose composure, but both did, near the end of the sketch.

Was Dragnet a cop show?