Eller was selected as the 6th overall pick in the 1964 NFL Draft by the Vikings from the University of Minnesota. The majority of his 225 NFL game career was with the Vikings (1964-78) but he did play for the Seahawks (1979).  He became a vital member of the Purple People Eaters, the team won the NFC Central title in 10 of his 11 seasons as a Viking. He also started at left defensive end in all four of the Vikings Super Bowl Appearances (IV, VIII, IX, XI).

Eller played in 209 games and started 201 games as a Viking, joining Jim Marshall and Mick Tingelhoff as the only players in team history to start 200+ games. He was named All-Pro 5 times and played in 6 Pro Bowls. He holds the Vikings record for total sacks with 130.0 sacks and is the only Viking to post 15+ sacks in a season multiple times. He was inducted into the Vikings Ring of Honor in 2002 and into the Pro Football Hall of Fame in 2004.