In his NFL career as a cornerback and safety, Hart had 15 interceptions. In 1969, he scored a touchdown on an 85-yard interception return against the Minnesota Vikings at Milwaukee County Stadium; it was the longest interception return in the NFL that season. As of 2011, his five defensive touchdowns were tied for fourth place all-time for the Packers. Hart was part of the Packer teams that won an unprecedented three consecutive NFL championships, which concluded with the first two Super Bowls.