The Dortmund captain struck in style just before the hour mark to seal a 1-0 win and move Jurgen Klopp's side four points clear of third-placed Bayer Leverkusen, who could only draw at Hannover on Saturday.
Kehl instinctively shot after Kevin Grosskreutz fed the ball into his path, with the 25-yard effort curling over Freiburg goalkeeper Oliver Baumann and into the back of the net.
The midfielder's first goal in any competition since April 2012 secured the three points for Dortmund, but they were made to work hard by the relegation-threatened hosts.
Christian Streich's side felt Dortmund defender Sokratis Papastathopoulos should have been sent off for bringing down the impressive Philipp Zulechner on the stroke of half-time.
Sokratis' challenge on Zulechner was the talking point of the first half, but the defender was only given a yellow card despite being the last man in defence.
Sunday's other fixture saw Mainz come from behind to claim a 1-1 home draw against Hertha Berlin as they failed to move into a UEFA Europa League spot.
