The organization described the incident as a "violent attack among orcas this morning, resulting in a serious wound to at least one of the animals."
PETA filed a complaint with the U.S. Department of Agriculture calling for an investigation.
The group said the visitor who filmed the incident said her 9-year-old daughter started crying after they saw blood in the water and wound marks on the orca.
In response, SeaWorld issued a statement that the behavior exhibited by the orcas has been documented in the wild as part of normal social interactions, and it resulted in only "minor and superficial abrasions that pose no serious health risk."
The park said PETA's video is "misleading and mischaracterized."