The footage showed Kim Reisner leaning over a fence to hit a horse, which refused to jump over obstacles.
The move cost competitor Anika Shloy the opportunity to win a gold medal, the AP reported.
The International Organization of Modern Pentathlon stated that it reviewed the video in which “it seems that Reisner is hitting a horse with a fist”, as well as that her action is “contrary to the rules”.
It is also heard on the recording that Reisner calls on Shloyev to hit the horse harder, adds the AP.
Suspension for Reisner applies only to the rest of the Olympic Games, which end on August 8.
Anika Shloy was also the subject of condemnation on social networks because, according to critics, she often used a whip.
Competitors in modern pentathlon ride horses they have never encountered before, and establishing trust with an animal in a short time is considered part of the competitive challenge.
German officials have previously said that the rules in that sport should be changed.