Davis wore number 87 during his career with the Packers. For 10 seasons, Davis anchored the Packers' defensive line, playing 138 consecutive regular-season games and part of 162 regular-season games for his NFL career. Davis was a member of all five of Vince Lombardi's NFL title-winning teams and played in Super Bowls I and II.
Davis played in an era when neither tackles nor sacks were official statistics. However, John Turney, a member of the Professional Football Researchers Association, reports that Davis had in excess of 100 sacks during his 10-year Green Bay career (1960–69), "possibly more than 120," including a minimum of 40 over the 1963–65 seasons alone. Davis himself is quoted as saying, "I would think I would have to be the team's all-time leader in sacks. I played 10 years and I averaged in the 'teens' in sacks for those 10 years. I had 25 one season. Paul Hornung just reminded me of that the other day." Davis earned All-Pro honors 5 times (1962, 64–67). He was voted to the Pro Bowl five times (1963–67).
Davis recovered 21 fumbles over his Packers career, which, more than three decades removed from his retirement, remains a team record. The Packers honored his retirement with a Willie Davis Day on December 21, 1969. Davis remains on the team's Board of Directors.
In the early 1970s, Davis worked as a color commentator on NFL telecasts for NBC. He was inducted into the Pro Football Hall of Fame in 1981. In 1986, Davis was named the Walter Camp Man of the Year. In 1987, he was given the Career Achievement Award from the NFL Alumni, and in 1988 he was elected to the Wisconsin Athletic Hall of Fame in 1988. In 1999, he was ranked number 69 on The Sporting News' list of the 100 Greatest Football Players.
Davis is a member of Kappa Alpha Psi fraternity. He received his MBA from the University of Chicago Graduate School of Business in 1968. He is a member or former member of the boards of Alliance Bank, Dow Chemical (1988–2006), Johnson Controls (1991–2006), K-Mart, L.A. Gear, Manpower (2001–), Metro-Goldwyn-Mayer (1999–), MGM Mirage, Rally's Inc., Sara Lee (1983–), Schlitz Brewing, and WICOR Inc. He has been president of All-Pro Broadcasting, operators of radio stations KHTI, KATY-FM, WLDB-FM, WLUM-FM, and WZTI since 1976.