Tyler, 63, lost two teeth and suffered facial cuts after falling in his hotel bathroom, Reuters reported, citing the South American nation's largest newspaper, ABC.
A man who identified himself as bellboy Gustavo Perez told local radio that Tyler slipped when he was taking a shower and "had a nasty fall."
Marcelo Antunez, a spokesman for the concert promoter GarziaGroup, told the media, "Mr. Tyler had a small accident that prevents him from staging the concert tonight."
He said Tyler "is fine, he's in his hotel but he's not able to do the concert," which was rescheduled for Wednesday.
The band is playing in Paraguay's capital as part of a rock festival that also includes Guns N' Roses.
Company head Nicolas Garzia tweeted yesterday morning that Tyler had become dehydrated due to gastrointestinal problems and had gotten "dizzy and fell in the bathroom, which gave him a cut lip and eyebrow and two broken teeth."
Paraguayan dentist Dr. Maria Bastos, who treated Tyler, told the Monumental radio station that the rock star was "friendly and humble" as he received two dental implants, and that he "surprised me with his cheerfulness," reported The Associated Press.