Last season's stop scorer Stefan Kiessling was quick to give Leverkusen the lead, taking advantage of indecision in the penalty area to head home after 23 minutes.
Freiburg responded brightly and levelled before the break through Mike Hanke, but their parity lasted just two minutes into the second half.
Sam got in on the act soon after, collecting a through-ball from Kessling before dispatching from a tight angle on the right flank.
Freiburg were then presented with a glorious opportunity to create a grandstand finish as the visitors were awarded a penalty.
Ruben Castro went close late on as Leverkusen pressed for a fourth, with Freiburg unable to prevent the hosts collecting all three points in a 3-1 success.