Eamonn Walker as Wallace Boden

After 12 seasons as a series regular, Eamonn Walker will depart the show in the season finale on May 22, titled “Never Say Goodbye.” He is expected to reprise his role as Wallace Boden in a recurring capacity in future seasons.

In a promo for the episode, Kelly Severide (Taylor Kinney) tells Boden, “You made 51 a family, Chief.” Joe Cruz (Joe Miñoso) adds, “And this firehouse a home.”

Kara Killmer as Sylvie Brett

Killmer joined the show in 2014 and took her final bow in a February 2024 episode that saw the beloved paramedic marry Matt Casey (Jesse Spencer) and move to Oregon to be with him.

“The writing’s been on the wall for a long time,” Kilmer told PEOPLE at the time. “Sylvie and Matt, their saga, that relationship had been building up for three years, and then Jesse exited the show [in 2021]. … She and Matt becoming a family is for sure the most natural, inevitable conclusion for the arc of her.”

Alberto Rosende as Blake Gallo

Alberto Rosende joined Firehouse 51 in season 8 as Blake Gallo, a fearless firefighter candidate who had lost his entire family in a fire as a child. Toward the end of season 11, he was reunited with an aunt, and in the season 12 premiere, moved to Michigan to be closer to his newly discovered relatives.

“When I decided to end my time with Chicago, it wasn’t easy,” Rosende wrote on Instagram. “The people I’ve met were truly special, the friendships I’ve made will last a lifetime, and the story I got to tell was one that made me proud.”

Jesse Spencer as Matt Casey

The heroic character left Firehouse 51 — and original cast member Jesse Spencer left the series — in 2021 with the show’s milestone 200th episode, when Matt Casey moved to Oregon to become the legal guardian for the teenage sons of his best friend Andy Darden, who died in the show’s pilot.

“This was a difficult decision because I have loved the show from the start but there are other things that I would like to do in the future, and there’s some family that I need to take care of,” Spencer said. “I was marking off these milestones and looking to the future … and it was time.”

Adriyan Rae as Gianna Mackey

Adriyan Rae joined Chicago Fire for season 9 as paramedic Gianna Mackey, who was longtime friends with Joe Cruz. She left at the end of the season for undisclosed personal reasons.

“All I can say is we love her, and I know she’s going to be great on some other series,” showrunner Derek Haas told Entertainment Weekly at the time. “She left 51 on great terms, so there’s a chance we could check in on her. We’re always looking for something to boost up a crossover! I don’t think we’ve seen the last of Mackey in Firehouse 51.”

Rae has since starred in two seasons of The Game on Paramount+.

Annie Ilonzeh as Emily Foster

Annie Ilonzeh first joined Chicago Fire as Emily Foster, a former medical student turned paramedic replacing Gabriela Dawson in Ambulance 61, in season 7. At the conclusion of season 8, she reapplied and was accepted.

She has since starred in a slew of movies, including Peppermint with Jennifer Garner and Vicious Affair on tubi.

Yuriy Sardarov as Brian Zvoncek (a.k.a. Otis)

After being wounded in the season 7 finale cliffhanger, Otis died heartbreakingly — and with best friend Joe Cruz by his side — in the season 8 premiere, signaling the end for original cast member Yuriy Sardarov.

“Thank you for the greatest 7 years of my life… #ChicagoFireForever,” Sardarov wrote on Instagram beside a poem he titled “Adieu” for the fallen fictional firefighter.

“I’ve known Yuriy since he was a junior in college in Michigan,” showrunner Derek Haas told PEOPLE at the time. “We did a movie together before Chicago Fire and it’s been awesome watching him develop into the actor that he is… It was tough making that call [to kill off Otis], but I knew it was right for the show. I tried to make it not meaningless.”

Otis is still frequently referenced on the show, as Firehouse 51 now has a statue in his honor outside and Cruz named his son Otis after him.

Sardarov has since guest-starred on The Rookie and FBI: International.

Monica Raymund as Gabriela Dawson

Chicago Fire began with Gabriela Dawson (Monica Raymund) having an unrequited longtime crush on Matt Casey (Jesse Spencer), which eventually led to their wedding during the show’s 100th episode in season 5. They were still married at the end of season 6 when Dawson left Chicago to help with rescue and relief efforts in Puerto Rico. She was seen briefly in the season 7 premiere saying goodbye to Casey.

Raymund appeared as a guest star in season 8 — and proved that the Dawsey sparks could still fly. “Dawson and Casey will always have an unbreakable bond, and their love is a special love that I think will forever stay alive,” she told Entertainment Weekly at the time.

Raymund has since remained in the Dick Wolf TV universe directing episodes of Law & Order: SVU, Law & Order: Organized Crime and FBI. She was also the lead in Starz’s Hightown for three seasons.

Steven R. McQueen as Jimmy Borelli

Steven R. McQueen’s firefighter candidate character Jimmy Borelli was first introduced in the season 4 premiere. The character had a pretty trauma-filled run for a season and a half: Jimmy’s brother died in a collapsed building and, early in season 5, Jimmy is badly injured in the line of duty, effectively ending his career and his time at 51.

The show’s co-creator Michael Brandt told Entertainment Weekly that this conclusion was a creative decision. “I think Steven has an incredibly bright future and deserves to be a bigger part on a show than probably we can give him,” he said. “We were, as writers, finding it hard to feed all the mouths that we have on the show. … We wanted to get a little leaner and meaner in terms of our storytelling and what characters we were focusing on. So Jimmy leaving was a byproduct of that.”

McQueen has since appeared in several TV movies, including Hallmark Channel’s Home by Spring.

Dora Madison Burge as Jessica Chilton

Friday Night Lights alum Dora Madison Burge’s Paramedic in Charge Jessica “Chili” Chilton received an uncharacteristically frosty reception when she arrived at Firehouse 51 during season 3. Of course, they all warmed to her soon after though, and she briefly dated Jimmy Borelli (Steven R. McQueen).

After Chili’s twin sister, Jellybean, was found dead in a Kansas City flophouse, Chili began a downward spiral and was eventually caught drinking on the job by Sylvie Brett (Kara Killmer). She ultimately faced disciplinary action and was fired, and Kelly Severide (Taylor Kinney) brought her to an AA meeting in her final moments on the show midway through season 4.

Matt Olmstead, the showrunner at the time, told The Hollywood Reporter that the decision to do this was “hard. We liked the actress a lot and she did a great job.”

Burge has since starred on What Would Diplo Do?.

Charlie Barnett as Peter Mills

Charlie Barnett’s Peter Mills was Chicago Fire‘s first firefighter candidate and quickly became a fan favorite, especially when he and Gabriela Dawson (Monica Raymund) dated in season 1. Sadly, he was written off the show in season 3.

“[The show] was a behemoth that I never really saw coming,” Barnett told PEOPLE in 2022. “I was thankful to be a part of it. I really was sad to be let go. It broke me for quite a long time.” Ultimately, though, he said the experience was “a blessing in disguise, and they all told me that.”

Barnett has since starred on the Netflix hits Russian Doll, YOU and Tales of the City.

Lauren German as Leslie Shay

The death of Lauren German’s Leslie Shay in the season 2 finale cliffhanger and season 3 premiere served as the show’s first devastating death and created a ripple effect that remains a part of the show (her name remains on Ambulance 61, for example).

“As storytellers, you have to be unsentimental,” showrunner Matt Olmstead told TVLine of the difficult decision to kill off Shay. “Sometimes, you have to do that to bring more storylines into a show, and that’s what we decided to do.”

German went on to star on Lucifer for six seasons.

Teri Reeves as Dr. Hallie Thomas

When Chicago Fire kicked off, Teri Reeves starred as Matt Casey’s on-off fiancé Dr. Hallie Thomas. Their relationship had newly rekindled toward the end of season 1 when she was murdered after uncovering that one of her colleagues at her clinic was part of a drug dealing ring.

Reeves has since appeared on shows including Once Upon a Time, Lucifer and The Punisher.