The film begins with Giselle Hammond arriving at a Mexican service station to buy cigarettes. The clerk receives a call and with his face away from the audience asks her Truth or Dare. Giselle reluctantly chooses dare and then proceeds to use lighter fluid and matches to set a middle aged Hispanic woman alight, apologising as she burns to death.
The film then jumps to an off campus university home housing three nineteen year old college students: YouTube vlogging philanthropist Olivia Barron, her best friend Markie Cameron who is struggling with her father’s previous suicide and remaining faithful to her boyfriend Lucas Moreno and their friendly, borderline alcoholic friend Penelope Amari.
Markie convinces Olivia to join her, Penelope, Lucas, Penelope’s pre-med boyfriend Tyson Curran, and Brad Chang, their gay friend hiding his sexuality from his father on a trip to Rosarito, Mexico.
In Mexico at a Havana Bar Olivia sways a drunken Markie away from a guy out of Lucas’ eyesight. Brad kisses a dancing guy and Tyson and Penelope proceed to kiss and drunkenly dance. At the bar Olivia runs into fellow student Ronnie who proceeds to harass her until a man seated alone at the bar intervenes on her behalf. The man introduced as Carter and continues to drink with her till the others join and all minus Markie and Lucas express wanting to not return their hotel yet.
Carter suggests a nearby place to hike to and leads them to the ruins of a mission. There Olivia comes across a broken urn with a skull engraving, undamaged photographs and a drunken Ronnie who has followed them in hopes of still hooking up with her or Markie. Carter initiates a game of Truth or Dare with the group plus Ronnie. The game oversees Tyson raising the question to Markie of Olivia’s hidden interest in Lucas, Ronnie giving Tyson a reluctant lapdance, Penelope kissing Olivia and Brad that admitting Carter is the only guy amongst them he is sexually attracted to.
The game ends when after choosing truth, Carter reveals he picked Olivia as a pushover target to trick her and her friends to the mission to offer them in his place in the game. As Carter leaves he explains to Olivia that the game will follow them and they must not refuse it.
The group leaves Mexico the next day. Messages of truth or dare reoccur around Olivia before finally facially morphed fellow students dare her at the school library to on the choice of truth reveal Markie’s deepest secret. Olivia yells out that Markie is constantly cheating on Lucas and Lucas who is seated with Markie hears and storms out. Markie rebuffs Olivia who tries to explain and follows him.
At a local college bar Ronnie attempts to flirt with a fellow female student Alexis and is met with rejection until her face morphs and she asks Truth or Dare. Ronnie chooses dare to impress her and is dared to expose his genitalia to the bar. As he goes to do so, negative reception from other female students prompts him to abandon the dare and he is taken control of with his face morphing. Ronnie then steps over a pool table ball falling and breaking his neck and back.
At Brad’s apartment Olivia, Tyson, Penelope and Brad see a video of Ronnie’s death. Olivia tries to explain that the game must be real and the rules Carter told her. Tyson remains skeptical and Lucas briefly arrives to grab his things ignoring Olivia. In the alley outside a graffiti message of Truth or Dare appears to Lucas as he hears a voice asking the same question and it becomes carved into his arm. Lucas chooses truth and on the phone to Olivia back at Brad’s tells how he’s considered what an alternative relationship with her would have been like instead.
The group gathers and tries to convince Markie the game is real. The game, playing in accordance to the order they played in Mexico, turns to Markie and going with dare is forced to break Olivia’s hand as she had threatened earlier, with a hammer.
At the hospital, using a female corpse in the morgue, Brad is asked and chooses Truth and is forced to come out to his father Officer Han Chang.
The next day at his med school, Tyson is presented with truth or dare by his interviewer as the others rush to him. Tyson selects truth and is asked whether he has been selling medicinal drugs from his studies. Tyson lies and is then forced to stab himself in the eye with his doctor pen before further impaling it into his head with a door headbutt.
The others research into Giselle Hammond, Carter and the Game utilising google and facebook. A saddened and drunk Penelope is put to bed by Markie and in the bathroom her reflection presents her with truth or dare. Penelope attempts to choose truth but is forced instead to do a dare of taking her vodka bottle and continuing to finish it while walking along the railing of the roof. Markie and Brad try to delay injury with her mattress, Lucas climbs up to her and Olivia tries to drive into the spike tipped side gate to prevent her death. Penelope survives the fall and the group receive a response from Giselle who Markie inboxed off a fake facebook account.
Meeting at a nearby warehouse Giselle reveals that she and her friends played the game and now is it down to her and friend Sam who had separated to get others to play in order to delay their deaths. Giselle reveals it has circled back to her and has the dare to kill Olivia as truth can only be chosen twice before it is dare for the third time.
Lucas wrestles with Giselle and Penelope is shot and killed instead. Having failed to kill Olivia Giselle is forced to turn the gun on herself and shoots herself in the head. The game then has Olivia in a dare as she refuses to choose truth. She has sex with Lucas prompting Markie to take off upset. Markie goes over her final video of her and her father which becomes controlled and gives her truth or dare. Choosing truth she reveals keeping her father’s suicide weapon as she contemplates killing herself.
Outside his apartment Brad is approached by his father who tries to discuss his love and support for him before his radio presents Brad with truth or dare. Unable to choose truth he is dared to withdraw his father’s gun and make him beg for his life. Brad hugs his father and withdraws his gun asking him to beg for his life. Brad is shot and killed by an approaching officer as Olivia and Lucas come running outside.
At the precinct Olivia learns that Carter is in fact the Sam from Giselle’s game. Once reunited with Lucas and Markie outside she is presented truth or dare. Olivia chooses dare and is dared to reveal what she is hiding from Markie. Olivia sits Markie down and informs her that the night her father died he was drunk and tried to force himself on her. Threatened with being reported to the police and Markie he committed suicide. A heartbroken Markie leaves the station and later at home is convinced not kill herself with the gun by Olivia.
Olivia and Lucas drive to Tijuana and meet with a mute woman and former nun who operated out of the church they played the game in the ruins of. She writes them notes informing them that they are dealing with a demon she summoned that possessed the the game of Truth or Dare and can be stopped by the last person to evoke the game sacrificing his tongue into an urn and sealing it with wax after an incantation in that place.
Olivia has Markie join her and Lucas and the three find Sam’s nearby location and confront him. After overpowering Markie and Lucas, Olivia forces him at gunpoint to journey with them back to the mission. There Sam begins the ritual and is about to sever his tongue when it becomes Lucas’ turn again. Lucas chooses dare and is asked to choose to kill either Olivia or Markie. Refusing to choose he accepts his death but is instead briefly possessed to stab Sam to death before he can finish severing his tongue for the urn. Lucas then slits his throat and dies leaving only Olivia and Markie.
Olivia figures a way to possibly survive and asks Markie as it is her turn again to choose dare and refuse it. Markie does so when dared to shoot Olivia. As Markie tries to shoot herself Olivia struggles with her and forces the shot to go off in her arm. She then proclaims to the demon that the dare is done and it is its’ turn. When the demon chooses truth she asks how she and Markie can survive. It reveals their last chance went with Sam though, like him, they can draw more people into the game.
With this Olivia records a video on her phone to upload to YouTube warning of the game and its’ rules, then ends by asking Truth or Dare initiating all watchers into the game.