After a turgid opening 45 minutes, Maximilian Philipp quickly broke the deadlock on his return to action.
Nils Petersen added a late second, though it could have been three if Vincenzo Grifo had converted from the spot.
First half fails to excite
Given the important of the game to both sides, it was no real surprise to see the two teams struggle to get going.
Set-pieces were all Freiburg could muster in the opening stages, despite their dominance in possession and territory. Tim Kister had to make a fairly unorthodox clearance to deny Florian Neiderlechner a free header on goal, but no-one could make the most of Vincenzo Grifo's deliveries.
Philipp Klingmann had the first major opportunity to come forward, after a quick counter saw him with space on the right. He opted to shoot instead of picking out the run of Aziz Bouhaddouz, which proved to be the wrong decision as he shot well wide.
Thomas Pledl also found joy out wide when skipping past the Freiburg defence, before having his cross palmed out by Alexander Schwolow. Robert Zillner fired the rebound over, when he really should have hit the target at least.
Despite hte best efforts of both, the remainder of the half was full of disjointed play due to the high number of fouls. This, combined with a strong midfield battle, prevented the pair from showcasing their passing games. A goal-less half was fair, given the even nature of the game.
Freiburg secure three points with second half showing
The second half quickly ended the wait for a goal, as Freiburg struck within five minutes of the restart. A deep free-kick found Marc-Oliver Kempf in the area, and he managed to bobble the ball down to Maximilian Philipp. The forward had just came on but took his chance well, scrambling the ball under Marco Knaller from close range.
This seemed to really knock Sandhausen's confidence, and saw Alois Schwartz respond. Korbinian Vollmann and Ranislav Jovanovic were brought off the bench, but it was not long after the attempts to kick-start their attack that defensive problems grew.
As Niederlechner went one-on-one with Knaller, Damian Roßbach hauled the Freiburg forward to the ground and prevented him from getting clean contact on the ball. Deniz Aytekin had little choice other than to award a penalty and produce the red card, but the hosts were given a slight reprieve as Grifo's penalty came back off the post.
Sandhausen never really threatened after that, and the visitors should have gone further ahead with Marc Torrejon heading over. Karim Guédé was denied by a smart Knaller stop at his near post, with Christian Günter slamming the rebound just past the post.
Günter would play his part in a Freiburg goal, however, as he set up Nils Petersen to seal all three points. A super break saw the left-back drive down the left before receiving Niederlechner's through pass and squaring for Petersen to tap into an empty net. It was deserved win in the end, as Sandhausen's previously powerful attack was made to look relatively toothless.