The Cleveland Browns of the NFL selected Martin in the second round of the 1950 draft. Led by an offense that featured quarterback Otto Graham, fullback Marion Motley and ends Dante Lavelli and Mac Speedie, Cleveland had won four championships in the All-America Football Conference leading up to the 1950 season, the team's first in the NFL. With Martin playing at defensive end, the Browns finished the 1950 season with a 10–2 record and beat the Los Angeles Rams to win the NFL championship. In a divisional playoff game against the New York Giants before the championship, Martin sacked Giants quarterback Charlie Conerly in his own end zone for a safety that helped secure a narrow 8–3 victory. The Rams scored a touchdown on their first play from scrimmage in the championship game, an 82-yard pass from Bob Waterfield to Glenn Davis. Martin was covering Davis and slipped on the play, although the Browns came back to win in the final seconds of the game.