In 1973, French street performer Philippe Petit is trying to make a living in Paris with juggling acts and wire walking, much to the chagrin of his father. During one performance, he eats a hard candy which was given to him by an audience member and injures his tooth. He visits the dentist and, while in the waiting room, sees a picture in a magazine of the Twin Towers in New York City. He analyzes the photo and decides to make it his mission to walk a tightrope between the two buildings. Meanwhile, he is evicted from his parents' house by his father, citing his lack of income and the fact that he's a street performer. Philippe returns to the circus that inspired him to wire walk as a child and practices in the big top after hours, but is caught by Papa Rudy, whom he impresses with his juggling skills. While performing one day, Philippe meets a beautiful woman and fellow street performer named Annie, and they begin a romantic relationship. He also explains that although he didn't know it at the time, she was his first "accomplice". He tells Annie about his dream to walk between the towers of the World Trade Center and she supports him and gives him a perfect place to practice at her music school. Philippe meets a photographer named Jean-Louis and befriends him, becoming Philippe's official photographer and second accomplice in his "coup".
Philippe requests Papa Rudy for tips and advice on knot tying and rope rigging, which Papa Rudy agrees to for compensation. After failing his first real performance by falling into a lake, Philippe decides to attempt to walk on the Notre Dame Cathedral in Paris to redeem himself. He succeeds with the support of Jean-Louis but is arrested in the process. Jean-Louis introduces Jeff, another accomplice who has a fear of heights, to Philippe and Annie, while explaining his idea to use a bow and arrow tied to a fishing line to get the cable across the Towers. Philippe and Annie then travel to America, setting the date for the walk as August 6, 1974. Philippe dresses in disguises to spy on the construction crews and scout out the locations, impaling his foot on a nail in the process. At one point, he meets a man who reveals he is a fan of Philippe's and saw him at Notre Dame. He introduces himself as Barry Greenhouse, a life insurance salesman who works in the building, becoming another member of Philippe's team. They also meet French-speaking electronics salesman J.P. and his friends, amateur photographer Albert, and stoner David. The gang goes over the plan several times, ending with the notion that Philippe must be on the wire before the construction crews arrive at 7:00 AM.
On the eve of the event, the gang encounters several speed bumps, such as being three hours behind schedule, guards on the premises and nearly dropping the heavy cable off the roof. However, they successfully string up the ropes and set the cables. Philippe begins his walk, explaining that everything around him faded once he started, except the wire and himself, and that for the first time in his life he felt truly thankful and at peace. He successfully crosses the gap between the towers while crowds below cheer him on. Once he reaches he has an urge to return, so he walks back again across the void. At one point he kneels to his audience and even lies down. The cops arrive, and threaten to remove him by helicopter if he doesn't get off but Philippe relentlessly continues to walk back and forth until he achieves the feat a total of six times. He is arrested on sight, with the police and construction workers commending him on his bravery. Philippe and his accomplices are eventually released and he decides to remain in New York, but Annie chooses to follow her dream, and return to Paris. The building manager gives Philippe a free pass to the observation decks of both towers, and Philippe gives a final look to the camera, with the Twin Towers in the background, as he says the expiry date on the pass was crossed out and changed to "forever".