A Muslim FBI agent of African-American descent, Darwyn infiltrates the LA sleeper cell using the name of Darwyn al-Hakim. A former Army Ranger, he quickly wins the cell's trust, though the stress of his job threatens to compromise his mental health.
- Becoming the Mask: Both Darwyn and his handlers are concerned that this might happen to him, especially in Season 2.
- Deep Cover Agent: For the FBI, spending time in prison in order to fabricate an appropriate backstory.
- Even Evil Has Standards: Invoked. Darwyn is, of course, a very good guy, but he pretends to be a terrorist with standards in order to convince Farik to take out a child prostitution ring.
- The Masquerade Will Kill Your Dating Life: Given that he's an FBI agent pretending to be a terrorist pretending to be a reformed ex-con, it's not surprising that his relationship with Gayle comes under a lot of strain.
- Scary Black Man: How he looks to his "allies" in the cell.
- Sixth Ranger Traitor: To the LA terror cell.
- Western Terrorists: He's pretending to be an American Islamic extremist.
- Where Da White Women At?: Played with. Nobody really has a problem with Darwyn's romance with Gayle on account of his skin color (or hers). The fact that he's a Muslim, however, worries her sister and brother-in-law, while Gayle being an "infidel" has Farik urging him to break it off.
The FBI agent who takes over Darwyn's case after Ray Fuller left the series. A hardline cop who follows procedure to the letter, she clashes with Darwyn, who prefers to improvise his plans as he goes along. Eventually they win one another's respect and trust.
- The Fundamentalist: A cadre of Islamist terrorist fundamentalists, from around the world.
Born Saad bin Safwan, Farik is the charismatic and brilliant leader of the LA sleeper cell. A former Saudi national currently masquerading as a Sephardic Jew in his civilian life, Farik is a fanatical, but cold-blooded zealot, who thinks nothing of mass murder so long as it meets his political ends.
- Archenemy: To Darwyn, though he doesn't know it at first.
- Bad Boss: In the first episode he has Bobby Habib executed for bragging to an uncle about their operation. He later murders Eddy Pangetsu (whom he forced into joining up with the cell in the first place)
- The Big Bad: Of both seasons of the show. Yes, the rest of al-Qaeda is out there somewhere, and Farik takes his marching orders from their higher-ups, but he's the one driving all the action in Sleeper Cell.
- The Chessmaster: Farik has multiple back up plans, and never lets any of the members of the cell know all the details for any of them. He typically gives each member of the cell a job to do, while keeping the master plan all to himself.
- Diabolical Mastermind: A terrorist variant.
- Even Evil Has Loved Ones: His wife and daughter.
- The Heavy
- The Leader: Of the LA sleeper cell. He's a combination of Type I and Type IV, running the cell through brains and sheer force of personality.
- Manipulative Bastard: Excels at playing the various members of the cell against each other, and preying on their insecurities in order to keep them in line.
A Bosnian Muslim who saw everyone he knew butchered by Serbs during the Yugoslavian Civil War, Ilija grew to hate the United States for not intervening in the conflict. Having been rescued by Farik's team of mujaheddin during the Civil War, he is now Farik's right-hand man. He spends his days undercover as a substitute math and science teacher.
- Beard of Evil
- Child Soldier: A former one.
- Doomed Hometown: His town was massacred by Serbs.
- The Dragon: To Farik.
- Freudian Excuse: He's got the most tragic backstory of any member of the cell. Given everything he's seen, it's not surprising he turned out the way he did.
- Karma Houdini: As of the end of Season 1
- Mad Scientist: He handles the technical side of Farik's plans.
- Politically Incorrect Villain: In addition to his religious fanaticism, he's got serious racial problems with Serbs and Croatians.
- Shell-Shocked Veteran: The Bosnian War broke Ilija in every way. He's still carrying all the pain around, and that's what drives him.
- Undying Loyalty: To Farik. It's his main trait.
- Brought into doubt by the end of the second season. He maintains that his loyalty remains beyond doubt. But it's clear in his facial expressions that he no longer wants anything to do with the man.
The financieer of the sleeper cell, operating out of Tijuna, Mexico. He enables the cell to operate by gathering revenue from pirated CDs, DVDs, narcotics and prostitution. Requires assistance from Farik to keep the funds flowing when the untimely death of one of their allies presents problems. Later, he brokers the exchange of explosives for heroin with a white supremacist gang, to equip for Youmud Din. In the aftermath of that failed attack, he succumbs to paranoia and goes off-grid to avoid the authorities. He wastes some of the ill-gotten funds on more vice for himself, before Darwyn reconnects with him and orders him to shape up.
A French skinhead who converted to Islam after falling in love with a Moroccan woman, Christian simply exchanged one form of extremism for another. A brutal thug, Christian is a deeply troubled man, who regularly seeks out one-night stands, even while bemoaning the failure of his marriage.
- The Alcoholic: Goes on a massive bender against strict Islamic doctrine banning the consumption of alcohol. Luckily for him, it's Tommy who finds him like this rather than Farik.
- Bald of Evil: Still has his skinhead haircut.
- The Brute: He's the muscle for Farik, and is regularly used to hurt or kill people the cell needs dead.
- The Casanova: Of a particularly predatory variety. He uses and discards women, typically blaming them for his own failings in the process.
- The Charmer: Christian can still turn on the charm when he needs to
- Drowning My Sorrows: After his wife leaves him.
- Everything Sounds Sexier in French: Uses this to try and impress women.
- The Fundamentalist: Though unlike the others, he may just see it as an excuse to hurt people.
- He-Man Woman Hater: Regularly blames the women he has sex with, referring to them as whores, and declining any personal responsibility for having slept with them.
- Hypocrite: He's an Islamist radical who nevertheless sleeps around, drinks, and otherwise violates even his own moral code.
- I Banged Your Mom: And brags about it to Tommy's face.
- Irony: An Islamist terrorist named "Christian".
- Kick the Dog: Joins Tommy in beating up a street preacher who annoyed them. And that's without getting into the time he slept with Tommy's mother.
- Neck Snap: Darwyn kills him this way
- Not So Different: Despite his claims to the contrary, Christian hasn't changed from his skinhead days, a fact that's pointed out to him by some white separatists they meet.
- Really Gets Around: If she's moving, Christian will try to have sex with her.
- Those Wacky Nazis: Was a Neo-Nazi before becoming an Islamist.
- Vitriolic Best Buds: With Tommy. They may bicker constantly, but spend all their time hanging out anyways.
- Western Terrorists
Thomas Allen Emerson
The son of two liberal college professors, Tommy Emerson seems to have converted to radical Islam just to spite his parents. A loose cannon who possesses all the maturity of an enraged teenager, Tommy is simultaneously violent and unsure of himself, which causes the cell some problems.
- Affably Evil: For all his poor social skills and anger issues, Tommy's probably the member of the group who tries the hardest to befriend the rest.
- Berserk Button: Pretty much anything having to do with his mother, honestly.
- The Brute: Like Christian, he's largely there to be the muscle.
- Calling the Old Man Out: Does this to his mother in the episode "Family". How fair he's being, we don't really know.
- Driven to Suicide: Blows himself up to avoid capture
- Even Evil Has Standards: He's not a racist, and calls Christian out on it whenever his old Neo-Nazi tendencies flare up.
- Hair-Trigger Temper: Setting Tommy off takes basically no effort.
- Kick the Dog: Beating up a Christian street preacher springs to mind.
- Mommy Issues: Loathes his mother, but won't hesitate to hit her up for money.
- No Celebrities Were Harmed: Based on John Walker Lindh, right down to the three names.
- No Social Skills: Tommy has a flat effect, speaks in a monotone, and avoids eye contact.
- Parental Neglect: His parents left him alone to be raised by their housekeeper, Theresa.
- Psychopathic Manchild: At the end of the day, Tommy's little more than a spoiled brat rebelling against his mother.
- Too Dumb to Live: Repeatedly has to be saved from his own stupidity. Even Christian is smarter than he is.
- Vitriolic Best Buds: With Christian. They argue and fight constantly, but spend all their time together anyway.
- Western Terrorists: He's American born and raised.
Khalid Noor al-Dibb
The initial leader of the second LA cell. Set up as a new version of Farik, his operations have hit a dead end with the funding from Mexico having dried up. Darwyn's return to the fold enables Khalid to make contact with Ziad and resume liquid cash flow. But Khalid's suspicions of Darwyn persist.
Wilhelmina "Mina" van der Hust
- Rape as Drama: Mina's visa is almost expired, threatening her job as a babysitter and therefore her status in the US and her eligibility for participating in the attack. The perverse father of the children she looks after turns the situation to his advantage, by baiting her with skeevy voyeuristic pictures of her at work. She is forced to let him rape her and perform oral sex on him or he will report her to immigration. Traumatised, she begs Darwyn to accelerate their date of martyrdom, and tells him about the story. A morally disgusted Darwyn then orders Benny to call in a beating of the man by the Maravilla, giving Mina revenge and a way out of her captivity.
- Seme: Serves as this, a volatile yet emotionally-shuttered top to Jason's Uke, as befitting his Armored Closet Gay extreme beliefs.
Benito "Benny" Velasquez
- Even Bad Men Love Their Mamas: Before his cell can set their attack in motion, he warns his mother and sisters to vacate LA for their own safety.
- Generic Ethnic Crime Gang: Unlike any other cell member throughout the series, he doesn't seem to be ex-military. He's an ex-member of the Maravilla Latino gang who abandoned them after his latest stint in prison. This is because he turns to Islamic extremism instead while inside, although Russell thinks this is just much of the same thing for Benny. He still springs the odd favour from the gang for the cell, and uses the cell to get back at his old gangland rivals so that they can obtain RDX explosives.
Abu "Karrar" Amin Mussa
AKA Karrar Bashir al-Abbani. The third leader of the second season's cell after Khalid and Darwyn himself. He is mysteriously transported by shipping freighter from the Gulf countries. He finalises the plans for a radioactive attack on LA, usurping the authority Darwyn had been enjoying over the cell.
- The Dragon: Farik's right hand man on the other side of the globe, enabled as such because Farik is in hiding after escaping US and Saudi custody.
- If You Kill Him, You Will Be Just Like Him: Why Darwyn manages to restrain himself from summarily executing Karrar, despite him trying to taunt Darwyn into doing it for his part to play in the death of Agent Serxner.
Other Recurring Characters
- Arranged Marriage: What her and Salim's parents want to set up. It doesn't take.
- The Beard: Functioned briefly as one for Salim, although he never got very close to her to uphold the lie.