Weaver was born Sylvester Laflin Weaver, Jr. in Los Angeles, California, the son of Eleanor Isabel (née Dixon) and Sylvester Laflin Weaver. He was of Scottish descent (possibly Clan MacFarlane), as well as of Ulster Scots and early New England ancestry. He was a great-great-grandson of Charles Laflin, a gunpowder manufacturer, who came to America in 1740 from Ulster, Ireland, settling at Oxford, Worcester County, Massachusetts. Charles Laflin and his family were living at Oxford, Massachusetts, when he purchased land in 1749 in the Southern (South-) village (-wick) part of the town of Westfield, Massachusetts. He was the brother of comedian Doodles Weaver. He graduated from Dartmouth College in 1930, where he was a member of Phi Beta Kappa and Phi Kappa Psi Fraternity. He also served in the United States Navy from 1942 through 1945. He married Elizabeth Inglis in 1942. She was born Desiree Mary Lucy Hawkins on July 10, 1913 in Colchester, Essex, England; and died on August 25, 2007 in Santa Barbara, California. She made her screen debut in Borrowed Clothes (1934) as well as having a number of small parts in some of Alfred Hitchcock’s early movies. She reached the high point of her career when she co-starred with Bette Davis in William Wyler’s movie The Letter. She retired from acting when she married in 1942. The couple were the parents of two children; Trajan Victor Charles and Sigourney (born Susan Alexandra).

Weaver worked for the Young & Rubicam advertising agency during the golden age of radio. In the mid-1930s he produced Fred Allen’s Town Hall Tonight radio show, and he then supervised all the agency’s radio programming. NBC hired him in 1949 to challenge the CBS network’s programming lead. At NBC, Weaver established many operating practices that became standard for network television. He introduced the practice of networks producing their own television programming, then selling advertising time during the broadcasts. Prior to that, ad agencies usually created each show for a particular client. Because commercial announcements could now more easily be sold to more than one company sponsor for each program, a single advertiser pulling out would not necessarily threaten a program. Weaver created Today in 1952, followed by Tonight Starring Steve Allen (1954), Home (1954) with Arlene Francis and Wide Wide World (1955), hosted by Dave Garroway. He believed so deeply that broadcasting should educate as well as entertain that he typically required NBC shows to include at least one sophisticated cultural reference or performance per installment—including a segment of a Verdi opera adapted to the comic style of Sid Caesar and Imogene Coca’s groundbreaking Your Show of Shows. Weaver did not ignore NBC Radio, either. In 1955, as network radio was dying, Weaver gave it one of the greatest adrenaline kicks in its history with NBC Monitor, a weekend-long magazine-style programming block that featured an array of news, music, comedy, drama, sports, and anything that could be broadcast within magazine style, with rotating advertisers and some of the most memorable names in broadcast journalism, entertainment and sports.

He was the developer of the magazine style of advertising which was very favorable towards the Networks. The sponsors would purchase blocks of time (typically one to two minutes) in a show, rather than sponsor an entire show. This style suited the networks. Like a magazine, a television network could now control what advertisements were being broadcast and no one advertiser could own exclusive rights to a particular show. NBC Monitor long outlived Weaver’s tenure running the network. Following disputes with chieftain David Sarnoff, Weaver departed. His ideas were either too expensive or too highbrow for company tastes. His successors (first, Sarnoff’s son, Robert; then, Robert Kintner) standardized the network’s programming practices with far less of the ambitiousness that characterized the Weaver years. In 1960, years after leaving NBC, Weaver displayed his frustration with the network in an article in the Sunday Denver Post. What once was the “Golden Age” of television in the early 1950s, slowly diminished by the end of the decade into the early 1960s when he claimed networks made a series of bad decisions. In the article he noted management problems within NBC, CBS and ABC: “Television has gone from about a dozen forms to just two-news shows and the Hollywood stories. The blame lies in the management of NBC, CBS and ABC. Management doesn’t give the people what they deserve. I don’t see any hope in the system as it is.” In 1985, Sylvester Weaver was inducted into the Television Hall of Fame. He died in 2002 of natural causes at his home in Santa Barbara, California at the age of 93.