• Brec Bassinger as Courtney Whitmore / Stargirl:
A high school sophomore who discovers a powerful cosmic staff and becomes the hero Stargirl. She is the leader of the new Justice Society of America. Bassinger did not look at the previous portrayals of the character by Britt Irvin on Smallville or Sarah Grey on Legends of Tomorrow because they were depicted as "older, more mature version[s]" of Stargirl. Bassinger added the series followed the comic Stars and Icicle more "in that she's young, high school, naive, which I wanted to bring that into this version of Stargirl."
• Yvette Monreal as Yolanda Montez / Wildcat:
One of Courtney's friends who becomes a member of the new Justice Society of America.
• Anjelika Washington as Beth Chapel / Doctor Mid-Nite:
One of Courtney's friends who becomes a member of the new Justice Society of America.
• Cameron Gellman as Rick Tyler / Hourman:
One of Courtney's friends who becomes a member of the new Justice Society of America.
• Trae Romano as Mike Dugan:
Pat Dugan's son and Courtney's stepbrother.
• Jake Austin Walker as Henry King Jr.:
The son of Brainwave and a student at Blue Valley High.
• Hunter Sansone as Cameron.
A student at Blue Valley High.
• Meg DeLacy as Cindy Burman.
The daughter of Dragon King and the most popular student at Blue Valley High who is determined to follow in her father's footsteps.
• Neil Jackson as Jordan Mahkent / Icicle.
A member of the Injustice Society.
• Christopher James Baker as Henry King Sr. / Brainwave.
A member of the Injustice Society.

Eight years ago, Jordan swears to his dying wife that he will ensure their son's safety. Courtney decides that she and Pat need to hunt down the Injustice Society's remaining members, starting with Icicle. Pat, however, insists that being a hero is far more dangerous than she understands. At school, Courtney meets aspiring magician Joey Zarick and art student Cameron Mahkent, Jordan's son. She also tries to stand up for classmate Yolanda Montez, who rebuffs her help. Meanwhile, Jordan visits fellow Injustice Society member, William Zarick, and sets up a trap for Courtney, correctly guessing that she will leap at any opportunity to catch him. A school bus gets caught up in their fight, and though Pat is able to save it from plunging into the water, he and Courtney are unable to save Joey from being struck by a truck. Enraged, William confronts Jordan, who murders him with his powers and has his elderly parents dispose of the body. Guilt-stricken by Joey's death, Pat takes Courtney to the old JSA headquarters and tells her to give up her identity until he says otherwise. Refusing to listen, Courtney steals the deceased JSA members' uniforms so she can find their successors. SourceWikipedia

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