PETA spokesman David Perle said Tuesday his group purchased 80 shares for more than $2,200 in last week's initial public offering of SeaWorld stock.
PETA officials say being shareholders will allow them to attend shareholder meetings and introduce resolutions.
The animal rights group says it wants SeaWorld to stop breeding and buying new animals at its parks in Florida, California and Texas. It also wants SeaWorld to release its whales and dolphins.
SeaWorld spokesman Fred Jacobs says the company anticipated PETA's purchase. He says SeaWorld will try to do for PETA what it does for any other shareholder: create investor value.