|“||You're a hero, Jennifer Jareau. You're my hero and your boys', and your team's, and all those other people that you saved. Don't you ever forget that.||”|
— Will in "Sick Day"
Little is known about Will's early life, other than his father, also named William, was a police detective for the New Orleans Police Department. His father died during Hurricane Katrina, which he refused to evacuate from while investigating a serial killer he was obsessed with. As an adult, Will followed in his father's footsteps and also became a detective.
Will is first seen in "Jones" investigating the serial killer case that initially belongs to his father. The killer is believed to have suffered the same fate, but when evidence to the contrary arises, Will takes over the case using the work his father had done (and a single word carved on the wall of his father's home). Will eventually calls in the BAU to assist him and they are ultimately successful in capturing the murderer. During the case, he and JJ are seen to develop an attraction towards each other.
Will reappears in "In Heat", where it is revealed that he has been romantically involved with JJ for over a year.
In "The Crossing", it is discovered that JJ is pregnant with their child.
In the season finale "Lo-Fi" Will tells JJ that he is willing to give up his job in New Orleans to have the baby with her. He also asks her to marry him, which she considers but ends up declining.
In "Memoriam", he is present at his son's birth and visits with most of the team at JJ's bedside. He leaves with everyone but Reid to get coffee. JJ introduces Henry to Reid and tells him she and WIll would like Spence to be Henry's godfather. She also says that Garcia is Henry's godmother.
As the BAU attempt to track down George Foyet in "100", Will and JJ take Henry to a pharmacy, where JJ finds out an important clue in the case. The clue helps the BAU find Foyet's address in Washington, D.C., but they find him gone. After Hotch's ex-wife, Haley is killed by Foyet, Will is one of those attending her funeral in "The Slave of Duty", where he offers Hotch his condolences.
In "There's No Place Like Home", Will and JJ are taking care of a sick Henry when she gets called into work. Will becomes unhappy with JJ's job and wishes she still worked at the Pentagon so she could have nights and weekends off. She offers to stay home but he tells her to go. While presenting the profile of a killer who strikes during tornadoes, Will calls and sends her text messages about an emergency concerning Henry. When she calls him back, Will tells her that he is at the hospital because Henry had a seizure. She makes plans to leave immediately but the weather has grounded all flights. She finishes the case and the episode ends with Will putting her on speaker phone so the two of them can read Henry a story at bedtime.
Will plays a major role in the two-part season finale "Hit" and "Run" (where it is revealed that he is still a police detective, but now works with the D.C. Metropolitan Police Department). He shoots and mortally wounds Oliver Stratton after his partner is killed by Oliver, earning him the hatred of Oliver's brother Chris. During the subsequent hostage situation at the Colonial Liberty Bank, in which three more people are killed, Chris asks for Will to enter the building. Feeling he is responsible for the deaths at the bank, Will accepts the call despite the protests of JJ and the rest of the BAU and calmly walks inside the bank, confronting Chris, who asks him his name. When Will states his name, Chris promptly shoots him twice. While a bulletproof vest protected him from one of the bullets, Will is hit in the shoulder and seriously injured. He is treated by two hostages before confronting Chris again, telling him that his partner Izzy Rogers was secretly planning behind his back. To convince him otherwise, Chris takes him to the gas lines, where they find Izzy setting a bomb. The bomb detonates, killing several hostages and allowing Chris and Izzy to flee with Will as a new hostage.
Chris and Izzy later force a medic at gunpoint to mend Will's wound before the latter kills the medic, and eventually Chris. Izzy then picks up Matthew Downs, a former Marine who happened to be one of the hostages treating Will's wound at the bank. They go to Will and JJ's house, where they find Henry under the watch of a neighbor. Will, being forced to be compliant, convinces the neighbor that Izzy is his cousin and that she will be babysitting Henry before leaving with Matthew, who takes him to Union Station. All the while, Downs rants on about how disconnected from the world he felt after serving several tours as a U.S. Marine. The two stop at Union Station; Matthew takes Will to a bathroom and straps a bomb onto him, intending to detonate it and kill Will and anyone else still in the building. However, he is found by Prentiss and she successfully defuses the bomb, while Matthew is shot and killed and Izzy is arrested before she can do any harm to Henry. At her request, Will proposes to JJ again and the two are married by the end of the episode at Rossi's place.
Will reappears in "Nanny Dearest", where he is once again left with Henry when JJ leaves to investigate a case. When JJ returns home after closing the case, she greets him with a passionate kiss that surprises him. The two take a look at a sleeping Henry before JJ closes the door to his bedroom.
Will briefly reappears in "200", where he informs the BAU about the connection between JJ and the FBI Section Chief Director Mateo Cruz when they both go missing. When they are both rescued, Will is seen with JJ at a bar with the rest of the BAU, and the two end the episode by kissing.
Will briefly reappears in "The Storm", where he and the rest of the family enter the BAU's office following the sudden arrest of Hotch. He spends the rest of the episode watching over his sons, as well as Hotch's son Jack.
Will reappears in "Sick Day", where he is taking care of his younger son Michael after he falls ill. Later, JJ comes home after a traumatizing child abduction case, and Will notices that she was disturbed by it. To help her vent, he allows her to recount the whole story while he listens.
- According to Erica Messer, an early draft of Run's script involved Will being killed at Union Station, but the idea was dropped due to the drama of Paget Brewster's simultaneous departure from the show as a main character.
- Season Two
- Season Three
- Season Four
- Season Five
- Season Seven
- Season Eight
- Season Nine
- Season Eleven
- Season Twelve
- "Sick Day"
- Season Thirteen
- Season Fourteen
- Season Fifteen
- Verified by Josh Stewart's offical Twitter account