Kramer played seven seasons (1957, '59-64) in Green Bay upon being drafted in the first round, with the fourth overall pick, in 1957. He compiled 2,594 yards receiving in 89 games, a yardage total that ranks second in team history for a tight end behind only Paul Coffman, and 16th in team annals overall.

Kramer's 170 receptions for the Packers rank sixth on the all-time tight ends list, and his 15 touchdowns rank fifth. Kramer did not play in 1958 when he joined the Air Force (he was also recovering from a serious leg injury at the end of his rookie season), but after returning to the Packers in 1959 he went on to post four consecutive 500-yard receiving seasons from 1961-64.

Kramer caught two TD passes from Bart Starr in Green Bay's 1961 NFL Championship victory over the New York Giants and then posted his most productive season in 1962, with 37 receptions for 555 yards and seven TDs. He was named first-team All-Pro by The Associated Press and also made the Pro Bowl that year. He was inducted into the Packers Hall of Fame in 1975.

Kramer came to Green Bay after a decorated career at the University of Michigan, where he is just one of five players to have his jersey retired in school history. He wore No. 87 for the Wolverines and No. 88 for the Packers.

At Michigan, Kramer handled a variety of roles as a two-time All-American on the football team – blocker, receiver, punter, kicker, linebacker, and even occasionally running back. A nine-letter winner as a multi-sport star, Kramer was also a three-time team MVP and leading scorer in basketball and a top shot putter and high jumper on the track and field squad.

Drafted by the Packers in 1957, Kramer was taken three spots after Green Bay selected Paul Hornung as the "bonus choice" and No. 1 overall pick. Following his time in Green Bay, Kramer played three seasons for the Detroit Lions (1965-67) and finished his NFL career with 229 receptions for 3,272 yards (14.3 avg.) and 16 touchdowns in 128 games.