The development team of The Last of Us spent more time selecting the actor for Joel than Ellie, as the chemistry between the two characters was imperative to the game. After Troy Baker and Ellie actress Ashley Johnson played alongside each other, the team realized that the former perfectly fit the role of Joel, despite the actor's young age. Creative director Neil Druckmann attributed Baker's voice and movement to the team's choice of casting him. Baker contributed greatly to the development of the character; for example, he convinced Druckmann that Joel would care for Tess due to his loneliness. When designing Joel's physical appearance, the team tried to make him look "flexible enough" to allow for him to appear as both a "ruthless operator in the underground of a quarantined city" as well as a "caring father figure to Ellie". His appearance was aimed to evoke "rural Americana", referencing values of self-reliance and ingenuity when facing hardship and deprivation. The team experimented with his appearance to determine his age in the game.
When writing Joel, Druckmann initially took inspiration from Josh Brolin's portrayal of Llewelyn Moss in No Country for Old Men (2007), which he saw as "very quiet, very cool under pressure". However, Baker's interpretation of Joel as a more emotional person evolved the character in a different way. Ultimately, the narrative became an exploration of how willing a father is to save a child; initially, Joel is willing to sacrifice himself, before evolving where he is willing to sacrifice his friends, until finally feeling that he would sacrifice all of humanity in order to save Ellie.
Druckmann felt that players, specifically parents, would be able to relate to Joel's character and his bonding with Ellie. Baker believes that Joel discovers morality throughout the game's narrative, working out the difference between loss and sacrifice, and his true personality begins to show. Druckmann became intrigued by players who discussed Joel's morality, distinguishing him as a hero or villain; Druckmann felt that Joel was only "a complex person who's made good and bad decisions", but allowed it to be open to interpretation. When auditioning for the role, Baker read a phrase on the character sheet that stated Joel had "few moral lines left to cross", which became the "anchor point" to the character for him. Baker found great difficulty in filming the game's prologue, which features scenes with Joel and his daughter Sarah, portrayed by Hana Hayes. Upon later viewing of the first day of footage from the scene, Druckmann felt that it could still be improved. When filming the scene again, Druckmann explained to Baker how to perform it, and felt that it was the best take upon doing so. Though Baker initially found the take too "mechanical", he retroactively realized that he had been trying to impress audiences by his acting, and that it was "not what the scene needed".