Character descriptions match the first character mentioned, if a cast member has more than one. For more detailed descriptions click the links.
- Grant Gustin as Barry Allen/The Flash/Barry Allen (Earth-2) - The main character of the show, an assistant police forensics investigator who accidentally gained superhuman speed after a particle accelerator went haywire and shocked him, causing him to become "The Flash".
- Candice Patton as Iris West/Iris West (Earth-2) - an investigative journalist and love interest of Barry.
- Carlos Valdes as Cisco Ramon /Vibe/Reverb - scientist and protegee of Harrison Wells at S.T.A.R. Labs and member of Team Flash, Cisco is known for cracking jokes at random.
- Tom Cavanagh as Harrison Wells (Earth-2)/Harrison Wells/Eobard Thawne - a brilliant scientist from Earth-2 intent on taking down Zoom.
- Jesse L. Martin as Joe West/Joe West (Earth-2) - father of Iris, and detective for the Central City Police Department. Also the adoptive father of Barry and former partners of both Eddie Thawne and Patty Spivot.
- Danielle Panabaker as Caitlin Sno /Caitlin Snow (Earth-2) - bio engineer at S.T.A.R. Labs and part of Team Flash.
- Keiynan Lonsdale as Wally West - Joe's son and Iris' brother who is also a skilled drag racer and engineer.
- Teddy Sears as Zoom/Jay Garrick/Hunter Zolomon - an evil speedster from Earth-2, determined to take over Earth-1 Central City, and eventually the multiverse.
- John Wesley Shipp as Henry Allen/Jay Garrick (Earth-3) - father of Barry, formerly incarcerated at Iron Heights Prison for the murder of Nora Allen.