Lynch played for the Giants between 1958 and 1966. For one year, prior to joining New York, he played for the Washington Redskins after entering the NFL out of Notre Dame University.
As a top defensive back, Lynch twice led the NFL in interceptions (9 in both 1961 and 1963). In 1963, he racked up 251 yards after interceptions, along with three touchdowns. He was named first-team All-NFL by several news publications for his efforts in 1963.
Over his NFL career, he snagged 37 interceptions for 592 yards, and returned 4 of those for TDs.