"Breeding is a natural, fundamental and important part of an animal's life and depriving a social animal of the right to reproduce is inhumane," the park said.
The panel's decision raised an array of questions, including whether the company would proceed with the project or raise a legal challenge, possibly on whether the commission overstepped its authority. SeaWorld said it was considering its options.
The vote followed a daylong hearing during which dozens of speakers argued for and against expansion. Although the permit involved a request to expand tank space, the discussion evolved into a wide-ranging debate over the conditions in captivity for the huge marine mammals, including breeding and the use of pharmaceuticals.
The commission that regulates land and water use along the California coast attached several conditions to the approval, including that no new whales from the wild will be kept there. SeaWorld says it hasn't captured wild orcas in more than 30 years.
Attendance at the California park has declined since the release of the population documentary "Blackfish" in 2013, which suggests SeaWorld's treatment of captive orcas provokes violent behavior. The company's stock price also has dropped over the past two years.
At the meeting, SeaWorld veterinarian Hendrik Nollens disputed what he called "outlandish accusations" from critics of the park. The whales are enriched and stimulated, he said, not stressed or depressed.