In 1998, Allen was slated to start at the left tackle position from day one of the season after starting final three games of 1997 at left tackle. In his first full season guarding Troy Aikman's , he earned consensus All-Pro and All-NFC honors. Allen became just the third player in league history to be selected to the Pro Bowl at more than one offensive line position when peers voted him to NFC Pro Bowl team at tackle. He earned recognition as part of an offensive line that allowed just 19 sacks for 110 yards in 493 pass plays for a season, the fewest in the NFL. Allen's blocking helped Emmitt Smith to record seven 100-yard rushing games and 1,332 yards on the season.