A sending off for Romain Brégerie was sandwiched by Alfredo Morales' opener and Moritz Hartmann's 10th goal this season.
However, the Lower Saxony outfit restored parity through Hiroki Sakai and Hiroshi Kiyotake to preserve their Bundesliga status for another weekend.
Ingolstadt down to 10, but go two-nil up
It was a slow start at the Sportpark, with Hannover largely camped in their own half despite requiring a win to give themselves any hope of staying up. Ingolstadt were trying to work the wings, but found a packed visiting penalty area hard to work around.
However, after 10 minutes, the lapse in concentration came that Ingolstadt had been working for. The ball was set for Danny da Costa to cross into the area, and Alfredo Morales came steaming in to bullet a header past the helpless Ron-Robert Zieler; the 'keeper was far from pleased that the American had ran in unmarked.
It looked like Hannover would come strong when Romain Brégerie was sent off for clipping the heels of Felix Klaus when running through, yet it only got worse for the Bundesliga's bottom club. Pascal Groß' free-kick from deep was sent into the area, and more poor marking saw Moritz Hartmann rise highest and head home.
Die Schanzer managed to play through a period of pressure from the Lower Saxony side, with Adam Szalai passing up a particularly good chance at the near post. The rest of the half was dominated by a series of fouls, though the home support were more than happy to see their side enter half-time with a two-goal cushion.
Hannover fight back to save their Bundesliga status for another week
Desperate to try and get something from the game, Daniel Stendel opted to call Iver Fossum off the bench for Alexander Milosevic. There was an initial spurt as Miiko Albornoz charged down the left after kick-off but he was denied by a strong block in the home defence. Ingolstadt, happy to sit on their lead, were slowly being placed under more and more pressure.
That would tell just before the hour mark, much to the annoyance of Ralph Hasenhüttl. A fine, flowing move from the visitors was capped off by Hiroki Sakai. The Japanese wing-back flew in on the right and strode onto Szalai's set-up, smashing home with an impressive finish.
Felix Klaus fired narrowly wide on the volley and Albornoz just over as the Hannover onslaught continued. Hasenhüttl's decision to bring on Almog Cohen looked to have solidified things, but Hannover had other ideas. A low, bouncing ball into the box somehow sat up nicely for Hiroshi Kiyotake, as the Japanese guided his half volley into the far corner - a massive miss from Lukas Hinterseer just moments before could have put the game beyond doubt.
The visitors prolonged the seemingly inevitable with the point, though Hannover would require Werder Bremen to lose every game while they win their remaining three fixtures. That would have to start with a game against Schalke 04 next weekend. Ingolstadt remain ninth, and need just one more point to assure an almost improbable fall into the relegation play-off place.