The promoted club have won only twice in 22 top-flight games this term and lie bottom of the table - 14 points behind fourth-bottom Wolfsburg but only four adrift of 18th-placed Hoffenheim in the relegation play-off place.
Buskens, 44, who led Furth to the second division title last season, was notified of the club's decision on Wednesday afternoon.
Club president Helmut Hack said on the club's official website: "We know what we have to thank Mike Buskens for, so it was a decision that was very difficult for us.
"We still have a chance to stay up. Therefore, we want to try to give the team a new impetus."
Under-23 coach Ludwig Preis and sporting director Rouven Schroder will oversee first-team affairs until a permanent replacement is appointed.
Schroder said: "This is only an interim solution, until we find a new head coach."
Furth, who lost 1-0 at fellow strugglers Fortuna Dusseldorf last weekend, host third-placed Bayer Leverkusen on Sunday.