The reopening accords with the Oklahoma government's reopening and recovery plan allowing businesses to reopen amid the coronavirus pandemic.
The park will operate at reduced attendance levels with a preview mode June 5-7 only for season-pass holders.
Six Flags says that it was implementing "extensive new safety measures and hygiene protocols" to protect park goers amid the coronavirus pandemic.
All customers over age 2 and all employees will be required to wear face masks covering the nose and mouth while in the park. The company says accommodations may be made on a case-by-case basis.
Customers without masks will be able to purchase them at the front gate.
"All government officials, along with city and county health departments, have been extremely supportive of our efforts to reopen in accordance with state and local guidelines," said Frontier City Park General Manager Trevor Leonard.
Leonard also said that outdoor attractions pose a "significantly lower risk of exposure" than indoor venues, as the theme park's attendees are not confined to one place for long periods.
The company's coronavirus security protocols include thermal imaging for temperature checks, screening technology for touchless bag checks and expanded mobile food ordering.
Six Flags shares at last check were 7.9% higher at $25.40. Six Flags stock has more than doubled since the beginning of April, when it closed below $11. In 2020 through Friday, the stock remained down 48%.