See the Cast of Criminal Minds Then & Now

Matthew Gray Gubler starred as Dr. Spencer Reid — the socially awkward boy genius of the Behavioral Analysis Unit — since the premiere of Criminal Minds on Sept. 22, 2005, and remained a key player in the series for all 15 seasons, down to the final episode on Feb. 19, 2020. Over the years, Gubler's Reid became one of the most beloved characters in the series. In 2015, the actor told Glamour it was "a real honor" to be on the long-running show.

"It's so bizarre it has been on for so long because in no way, shape or form does it feel like that. It still feels like day two," Gubler said. "'Family' is the only thing I can think of to sum it up."

Kirstin Vangsness, who played eccentric tech analyst and communications liaison Penelope Garcia, was on Criminal Minds for seasons 1 through 15 and was the only cast member to also appear on both of the series' spin-offs, Criminal Minds: Beyond Borders and Criminal Minds: Suspect Behaviors.

Penelope served as a key member of the crime-fighting team but also provided some much-needed comedic relief, particularly in her ongoing flirtation with Derek Morgan (played by Shemar Moore). Vangsness told E! the show was a "wonderful, joyous, friendly and creative experience."

A.J. Cook was just 27 when the show premiered in 2005, and she remained on it through season 15 as special agent Jennifer Jareau, aka JJ. The Canadian actress, now 42, has been through a lot during that time, including being pregnant with her first child during season 3. In an interview with TVLine, Cook said the series end was "nostalgic."

"The way to really put it in perspective is that we all went to kindergarten together, and now we've graduated high school," she said. "It's like we're going off to college, and to wrap up as best you can all the experiences we had in that amount of time is a tough thing to do."

Paget Brewster's character, special agent Emily Prentiss, had a wild ride on Criminal Minds. Brewster joined the series during season 2 and appeared through season 7. She then took a break from the CBS show when her character left the BAU for a job at Interpol.

After several guest appearances in the years following, Brewster returned for season 12 as a series regular and has stayed on through the show's end.

Shemar Moore played heartthrob Derek Morgan for seasons 1 through 11 and appeared as a guest during both seasons 12 and 13. Fans lamented Moore's departure from the show, but the actor said he was seeking more "balance" in his life in a 2016 interview with TVLine: "I love what I do for a living, I love it from 'action' to 'cut', but I also want to walk my dogs, travel, get married, have kids."

Moore has since starred in the CBS series S.W.A.T. as a Los Angeles S.W.A.T. lieutenant.

Joe Mantegna's David Rossi joined Criminal Minds during season 3 and his character quickly took on a father figure role among the group of FBI agents. Mantegna, 72, posted on Twitter after filming his final scene for the show in May, calling the series a "truly wonderful experience."

"I will miss playing David Rossi, and I'll miss the wonderful writing that brought him to life, but mostly I will miss seeing my fellow cast mates and our fantastic crew every day," the actor wrote. "It may seem a cliché to say we're like family, but it's so very true."

Aisha Tyler appeared as Dr. Tara Lewis for seasons 11 through 15 of Criminal Minds. The actress, who spent 6 years as a host on The Talk, has also directed several episodes of the show. In 2019, she told Parade that the series close was "bittersweet."

"It's bittersweet that Criminal Minds is coming to an end. But I'm grateful that unlike some shows, we were given the time to plan a proper series finale," Tyler said of the show's end. "We are all trying to savor our last moments on set."

Adam Rodriguez began playing Luke Alvez, a special agent in training, in season 12. But Rodriguez had some experience playing a member of law enforcement before he joined the cast of Criminal Minds, having played Eric Delko in 10 seasons of CSI: Miami.

The actor also starred alongside Channing Tatum in Magic Mike and Magic Mike XXL, and has appeared in Ugly Betty, Jane the Virgin and Empire.

Daniel Henney appears in both Criminal Minds and its spin-off series, Criminal Minds: Beyond Borders. He joined the show in 2015 to play special agent Matt Simmons. Henney began his career as a model in Korea and made his U.S. acting debut in the film X-Men Origins: Wolverine.

Henny stayed on Criminal Minds through its 15th and final season.

Mandy Patinkin served as the original show lead in seasons 1 and 2, but left suddenly before season 3. Patinkin played special agent Jason Gideon, who retired from the BAU following the death of his girlfriend.

Since leaving the show, Patinkin has acted in several films and went on to star as Saul Berenson on Homeland from 2011 to 2020.

Lola Glaudini only stuck around for the first season of Criminal Minds, playing Elle Greenaway, who wound up in a shootout in her final episode. In real life, the Sopranos actress reportedly left because she wanted to move back to the East Coast from Los Angeles.

Since then, Glaudini has appeared in the Marvel series Agents of S.H.I.E.L.D. on ABC.

Thomas Gibson played troubled workaholic Aaron Hotchner for seasons 1 through 12. Gibson was fired from the show following a physical altercation on set. "I feel like it took years to make a good reputation and a minute to damage it," the actor told PEOPLE in 2016 of the incident, which involved a disagreement between him and writer-producer Virgil Williams.

"My pride and reputation are hurt, but in the end I know the good work is what people will remember," he said. "I just need more opportunities to do good work and be a good guy."