The 51-year-old joined from 2. Bundesliga side Jahn Regensburg in July but has overseen a torrid start to the 2019-2020 campaign after Cologne's promotion from the second tier.
He managed just two wins from his opening 11 Bundesliga games at the helm, with Saturday's (AEDT) 2-1 home defeat to Hoffenheim proving the final straw for the club's hierarchy, despite it coming as a result of a controversial late penalty for the visitors.
Beierlorzer told the club's official website: "I regret that I wasn't able to bring Cologne the desired sporting success in the four months I was here. I felt completely at home at this great club. In a good working position, I was able to work with the team constructively. For the rest of the season, I wish the team and the club all the best."
Sporting director Frank Aehlig added: "I regret that we've had to take this step, because we value Achim Beierlorzer very highly. However, the hoped-for sporting success hasn't been achieved so far and it's our job to do everything to ensure we achieve our goals."
Cologne has placed Andre Pawlak and Manfred Schmid in temporary charge.