"We have decided to part ways," a club official told Reuters.
Stanislawski had joined from St Pauli in the summer but had seen his new team record only one league win in the last 10 games.
The club's major investor Dietmar Hopp had demanded a spot in the German Cup semi-finals to make amends for their bad league run but instead they went out 1-0 to second-tier Fuerth.
The official said an announcement would be made later on Thursday.
Hoffenheim are eighth in the league on 24 points from 20 games.
The battle to avoid relegation is heating up in the Bundesliga with 11 teams locked in a fight for survival separated by seven points just past the season halfway mark.
In one of the mostly tightly packed lower halves of the table for years, bottom-placed Freiburg, on 17 points, are just two wins and a draw away from Hoffenheim in eighth place.
"There is a lot of unrest in the club," said Hoffenheim keeper Tom Starke after their surprise Cup exit, adding that the team had become a laughing stock.
"The whole club is shaking and it is internal problems that we ourselves created. The whole of Germany is laughing at us."
He also warned of the danger of relegation given the unrest.
"The danger is there because we are not pulling together and there is too much unrest," he said. "There is no reason to pretend things are good."