Joselu's stoppage-time strike earned a point for Hannover and leaves Freiburg bottom of the Bundesliga over the Christmas break.
The visitors thought they had taken the lead inside the opening 15 minutes when the Spaniard's well-struck shot was met with a flying save from in-form keeper Roman Burki.
Within seconds, the hosts were threatening a breakthrough of their own with Vladimir Darida firing narrowly over the crossbar.
Freiburg then had a lucky escape midway through the first half as Jimmy Briand's low header beat Burki, but came back off the woodwork.
The home side then took the lead on the brink of half time as Mike Frantz turned Christian Gunter's cross home to the delight of the majority inside the Mage Solar Stadion.
They nearly added a second within moments of the restart as Felix Klaus's effort came back off the woodwork before Darida's follow up was saved by Ron-Robert Zieler.
Freiburg did double their advantage with nine minutes remaining as Marc-Oliver Kempf headed home from Jonathan Schmid's corner.
The defender quickly went from hero to villain in the space of two minutes as Kempf's failed clearance gifted a chance to Leonardo Bittencourt and the forward duly pulled a goal back for the visitors.
Freiburg were within seconds of victory before Joselu was gifted a chance to score by keeper Burki's poor kick, which the forward tucked away, netting for the fifth successive game to take Hannover into eighth.
