He started his gymnastics career at the club in his hometown of Frankfurt an der Oder before moving to Berlin in 1860, where his talents were soon noted and he was selected to represent his country.
In Athens, as well as helping Germany to secure victory in both of the team events, which were contested on the parallel bars and the horizontal bar, he also took first place in the individual horizontal bar, was runner-up in the pommel horse and rings, and finished third in the vault.
After his return to Germany he and most of the other German gymnasts were suspended, because the Deutsche Turnerschaft, the governing body of German gymnastics, had boycotted the Olympic Games on the basis that competition was not in the spirit of the discipline.
Weingartner decided to return to his native Frankfurt and took up a post managing the open-air swimming pool that had been founded by his father on nearby Ziegenwerder Island. Tragically, he later drowned while trying to rescue a person who had fallen into the River Oder.