Matthew "Matt" Simmons is a Supervisory Special Agent with the Behavioral Analysis Unit. He was previously attached to the FBI's International Response Team (IRT), which was featured in Criminal Minds: Beyond Borders. He and the rest of the IRT were introduced in Beyond Borders. He reappeared as a main character in Season Thirteen when he joins the BAU following the disbandment of the IRT.
Simmons was born in Carson City, Michigan to a Caucasian father and a Korean mother. Because of his mixed ethnicity, his paternal grandparents ostracized him. In his adult life, he joined law enforcement in Detroit. He and his wife Kristy have been together for ten years and have four children: two sons Jake and David, and twin daughters, Chloe and Lily; this fact has caused jokes about him being a "breeder". He is an FBI agent and specifically worked for Jack Garrett and the International Response Team. Through this job, Simmons has a prior history with Derek Morgan and Jennifer "JJ" Jareau. He is a military veteran who has seen combat overseas, presumably in the Middle East. This allowed him to hone his split-second decision-making skills. Hence, he is usually the quickest of the team to draw up a preliminary profile on an unsub.
With the IRT
Simmons is first seen coming out of the SUV with Jack and Lily Lambert, who are all on their way to the plane. There, they meet up with Morgan and JJ, who learn about Matt's newborn twin daughters. They then board the plane and discuss the case during the flight to Barbados. During the investigation, Simmons is paired up with Morgan and JJ. He delivers the profile along with the other members of the BAU and the International Unit. Afterwards, they looked up on the computer and eventually identify the unsub as Jerry Tidwell. The following night, Simmons uses a speedboat to get to Tidwell's boat, where he is holding the Sullivan family captive. After Tidwell is killed and he is informed about the son Nick being thrown overboard, Simmons locates Nick on a small raft, rescues him, and brings him back aboard Tidwell's boat. Back in Quantico, Simmons, along with the others, watch as the Sullivans are reunited with their relatives.
Simmons reappears in the episode, working alongside Clara Seger when they are called in by Prentiss to help Reid, who was arrested in Mexico for drug possession and the murder of Nadie Ramos. At the time, the IRT was investigating another case in Costa Rica. The two IRT agents arrive at the local jail Reid is being held in and try to stop his transfer to Prisión de Máxima Seguridad El Diablo. Simmons tells Reid about a new lead, adding that there is no contraband on him. When Reid asks what were inside the vials of experimental medication he had, Simmons gives him a list of the medication's ingredients. This helps the BAU pinpoint Nadie's hometown. Just then, the Mexican police are given orders to transfer Reid to El Diablo. However, the agents are able to stop the transfer and have him extradited back to the U.S. after they realize the victim has dual American-Mexican citizenship. Afterwards, Simmons is seen onboard the BAU's plane, thanking Rossi for having him and Seger flown back to Quantico.
Criminal Minds: Beyond Borders
Simmons is portrayed as the muscle of the team, similar to the role Morgan played on the original show.
With the BAU
- His sidearm was a SIG Sauer P226R. In Season Two of Beyond Borders, both he and Jack Garrett, who also carried a P226R, switched to older models of the same weapon without a rail. Simmons continued to carry this weapon during the hunt for Peter Lewis and in the first few episodes of Season Thirteen. However, in Dust and Bones, he is once again seen using the newer P226R model.
- In the Beyond Borders episode Love Interrupted, there is a scene in which Simmons rides a motorcycle instead of Garrett's vehicle. Daniel Henney, the actor who plays Simmons, renewed his motorcycle license and did the scene himself instead of a stunt double.
- It was mentioned in the backdoor pilot that his four children were all under three. However, the boys were recast as slightly older, likely between the ages four to six, when Beyond Borders was picked up.
- Simmons was written to be of partial Korean descent. Likewise, Henney is biracial: his father is of Irish descent and his mother is Korean.
- Like Derek Morgan, he usually kicks doors down and storms in. (Wheels Up)
- His first job in law enforcement was in Detroit, likely at the local FBI field office (Blue Angel).
- He has knowledge about the toxicity of venom produced by different species of snakes, likely honed from years of international travel with the IRT. (Dust and Bones)