Aaron Pierce on Day 7
|Portrayed by||Glenn Morshower|
|Seasons||1, 2, 3, 4, 5, 6, 7|
|First appearance||Day 1: 1:00 AM – 2:00 AM|
|Last appearance||Day 7: 7:00 AM – 8:00 AM|
 Day 1
Agent Aaron Pierce is put in charge of the Secret Service detail during Day 1 to protect Senator David Palmer, when his life was in danger from a possible assassination attempt. Agent Pierce first meets Jack Bauer when Senator Palmer was hosting a breakfast.
 Day 2
Agent Pierce is the head Secret Service Agent to protect President David Palmer during Day 2. When President Palmer is removed from office when the 25th Amendment is invoked, he is in charge of guarding Palmer. Since Pierce is very loyal to President Palmer, he believes he shouldn't have been removed from office. Palmer asks for his help, to get a satellite phone, so he could contact Jack Bauer. Pierce agrees and gets the phone for him. But when Mike Novick finds out, he places Pierce under arrest. Once President Palmer is back in power, he drops the charges on Pierce.
 Day 3
In Day 3, Aaron Pierce is in charge of protecting President Palmer when Los Angeles is targeted for a biological terrorist attack. When the virus is released in the Chandler Plaza Hotel, located in LA, Pierce tells Palmer that he'll be transported to Washington. But Palmer refuses to leave Los Angeles. Palmer eventually convinces Pierce for him to stay in LA and Pierce continues protecting him while he's in LA.
 Day 4
In Day 4, Aaron Pierce is now serving under President John Keeler, and later President Charles Logan when Air Force One is shot down and President Keeler is in critical condition. When President Logan decides to bring in former President Palmer as a consultant, Pierce is honored with protecting Palmer as well. At the end of Day 4, Pierce reveals to Palmer that the woman they'll be granting immunity to is Mandy, the woman who tried to assassinate him at the end of Day 2.
 Day 5
Aaron Pierce is in charge of the Secret Service Detail to protect President Charles Logan during Day 5. When First Lady Martha Logan goes missing, he finds her looking through files to find the transcript of the conversation she had with David Palmer. He escorts her back to the retreat.
When Jack Bauer comes to the retreat to meet with Mike Novick, Agent Pierce keeps guard on Jack when he gets detained. Jack tells Pierce the reason he was meeting with Novick was because that Walt Cummings was involved with the nerve gas conspiracy and the assassination of David Palmer. Pierce agrees to help Jack and lets him out of custody and leads him to President Logan and Walt Cummings.
When the Suvarov's motorcade is attacked by Vladimir Bierko's men, Aaron Pierce is able to kill the remaining men and save the Suvarov's as well as Martha Logan from being attacked. After the attack, Martha tells Aaron that her husband knew about the attack and didn't stop it. When back at the retreat, Martha thanks Aaron and they hold hands, Mike Novick interrupts the moment and asks to speak with Aaron. Aaron tells Mike that nothing happened.
Later on, Wayne Palmer contacts Aaron to meet with him, he agrees and sets up a meeting place. Aaron starts to look for Wayne when he hasn't arrived, Wayne tells Aaron that men were trying to kill him and they head back to the retreat. Wayne tells Aaron that Evelyn Martin has information about the conspiracy of the death of David Palmer. Evelyn reveals to them that she'll only give the information if her daughter is returned to her, since Christopher Henderson had her kidnapped. Aaron stays at the retreat, while Wayne and Evelyn meet with Jack Bauer to aid them in rescuing her daughter. When Jack finds out the man behind the conspiracy is President Logan, he phones and warns Agent Pierce to watch his back since he now knows the truth
When Martha starts to become suspicious of her husband, she asks Aaron to meet with her. When she goes to meet with him, he is not there. She finds his phone on the ground. She later asks her husband where he is, he says he was transferred to Washington.
We later learn that Pierce is actually being held captive by President Logan because of what he knows. When Aaron refuses to keep the truth hidden and believes he'll be a concern, he orders Agent Adams to kill Aaron. When Martha is looking for Aaron, she spots him about to be killed by Adams. While she's talking to him, Aaron is able to knock Adams to the ground. As their fighting, Martha grabs Adams' gun and shoots him. Pierce then puts his body in the trunk of the car and tells Martha to contact Mike Novick and tell him what's going on. When Mike meets with Martha and Aaron, they reveal that President Logan is involved in the conspiracy. Mike agrees to help and decides to get Aaron off the retreat for his safety. Before he leaves, he says goodbye to Martha.When they're off the retreat, he contacts Jack Bauer and tells him Mike can be trusted. He informs Jack that President Logan will be delivering a eulogy at Palmer's funeral. Since President Logan will be leaving soon, they bring Martha Logan into the plan to stall her husband. Aaron meets up with Jack and gets him access into the Secret Service building. With the help of Mike Novick and Chloe O'Brian at CTU, they are able to get Jack as the pilot on the plane with President Logan. Aaron wishes Jack luck before he leaves. President Logan is brought to justice at the end of Day 5.
 Day 6
In Day 6, Aaron is no longer a Secret Service Agent. He is living with Martha Logan in what appears to be a type of assisted living facility. While bringing groceries to Martha, Charles Logan calls and asks if he can speak to Martha. Aaron is reluctant because of Martha's unstable mental health. However, he convinces Aaron it is necessary he speak to her. Martha eventually agrees for Charles to come. When Charles arrives, he offers to shake hands with Aaron, but he doesn't comply. Aaron tries to keep Charles and Martha calm through their intense discussion. However, he is unable to stop Martha from stabbing Charles in a fit of rage. As Charles is taken away by the ambulance, Aaron convinces Martha to call Anya Suvarov regarding the situation at the Russian Consulate.
 Day 7
When Benjamin Juma and his men attack the White House, Aaron protects Olivia and are able hide from Jum'a men for sometime, but eventually they're found. Aaron is shot by one of Juma's men but is able to kill him. He then tells Olivia to try and send a signal to the outside by using Morse Code with a flashlight. While trying to send the message, she is captured by Udo and other soldiers and brought to Juma with the other hostages.
When Bill Buchanan sacrificed himself by setting off the explosion inside the White House, Aaron protects the President and her daughter, escorting them out of harms way. Once Juma and all his men are killed, Aaron is gets medical attention for his gunshot wound in the shoulder. Olivia thanks Aaron for saving her life and asks him why he retired. She asks if it had to do with what happened to Martha Logan, he tells her he doesn't want to talk about it, but accepts her thanks.
After Aaron finished submitting his statement regarding the attacks on the White House, he is approached by Olivia Taylor who was appointed the interim Chief of Staff by President Taylor. He is asked by Olivia to stay on and be reinstated to be her head of security. He initially declined the offer, but later accepted when he is told by Olivia that he is the only person she trusts. Later on, Aaron drives Olivia to meet someone at a hotel, unknown to him that it's a reporter, Ken Dellao. When they arrive at the hotel, he insists on checking the room before she enters, but Olivia refuses and tells him to wait outside. After about half an hour, Olivia exits the room and receives a call from her mother requesting her to return to the White House. They both leave the hotel, but Aaron seems suspicious of Olivia's actions.
- Aaron is the only character besides Jack Bauer to appear in every season to date.