A pre-credits scene shows an episode of the popular game show 'To Tell the Truth' set in 1977 where three contestants appear claiming to the panelests to be the legengary Frank Abagnale Jr. (Leonardo DiCaprio) who impersonated an airline pilot, a lawyer, and doctor, as well as scammed people on three continents for millions of dollars... all before reaching the age of 19.
The film begins in 1969, with FBI agent Carl Hanratty Jr. (Tom Hanks) arriving at a French prison to meet the flu-stricken Frank Abagnale Jr, who attempts to escape from the prison prior to his extraction to the USA for a series of crimes.
The scene flashes back to six years earlier. 16-year-old Frank Abagnale Jr lives in New Rochelle, New York with his father Frank Abagnale, Sr. (Christopher Walken), and French mother Paula (Nathalie Baye). Frank's father cons a woman into lending him a suit for Frank Jr., who later acts as a driver for Frank Sr. in a ruse to get a loan from Chase Manhattan Bank. When the loan is denied (due to a series of IRS tax frauds by Frank Sr.), the family is forced to move from their grand home to a small apartment, with tension building within the family.
Frank soon realizes that his mother is having an adulterous affair with his father's friend Jack (James Brolin) and feeling that he will not fit in at his new school, poses as a substitute teacher in his French class for a short time. Eventually trouble builds between Frank's mother and father, who file for divorce and ask Frank to choose who he will live with. Horrified, Frank runs away from home, using checks that his father had given him. When Frank runs out of money, he begins to use confidence scams. Frank's cons grow ever bolder and he even impersonates an airline pilot. He forges Pan Am payroll checks and succeeds in stealing over $2.8 million by staying in fancy hotel suites, and eating at expensive restaurants, with the bills going to Pan Am.
Meanwhile, Carl Hanratty, the nearly humorless but persistent FBI agent, begins to track down Frank in spite of his superiors not attaching much importance to the case (as most of them do not take bank fraud seriously). Tracking Frank to a hotel, Carl discovers to his surprise that he is still a resident there and breaks into his room to arrest him. Emerging from the bathroom and knowing only that Carl is from the FBI, Frank pretends to be Agent "Barry Allen" of the United States Secret Service and brazenly claims to have just caught the suspect himself. It is not until after Frank has escaped from the room that Carl realizes he has been fooled.
Frank soon attempts to use the money that he has stolen to find a way to reunite his divorced parents. He invites his father to a fancy restaurant, and gives him the keys to a brand-new Cadillac. Frank Sr. explains that he can't accept the gift, since the IRS are still watching him, and makes an attempt to put a positive air to the meal.
Some months later, on Christmas Eve, while Carl is working in the office late and alone, Frank calls him to apologize for tricking him back at the hotel. Carl announces that it doesn't work that way and, to Frank's horror, Carl realizes the reason for the call: Frank has no one else to talk to. Frank hangs up, and Carl continues to investigate. He later discovers that the name Barry Allen is from The Flash comic books and that Frank is actually a teenage minor, which explains why they have been unsuccessful in finding a record of him.
Remembering that Frank had made a reference to the New York Yankees, Carl has his men check for runaways in New York. Their search eventually leads them to Frank's mother, who has now remarried. After seeing Frank's yearbook picture, Carl now knows who his suspect is.
One year later. Frank has not only changed from impersonating a pilot to impersonating a doctor (complete with a forged Harvard Medical School degree) in Georgia, but is romancing Brenda Strong (Amy Adams), a Southern belle who works as a hospital nurse. He proposes marriage to her, at least partly to try to engineer a reconciliation with her parents who have disowned her since she had an abortion. The two travel to meet her parents in Louisiana. Announcing to them not only that he is like them a Lutheran but that he is a qualified lawyer as well as a doctor. Frank soon joins Brenda's father (Martin Sheen) as an assistant prosecutor after passing the Bar exam.
Frank soon decides to marry Brenda, and decides to tell his father. It is here that Frank Sr. (now working as a US Postal worker) informs his son that Frank's mother has remarried, devastating Frank. After Frank leaves his father for good, he calls Carl, wanting the chase to end in the wake of his wanting to settle down. Carl informs Frank that this is not possible, since Frank has stolen some $4 million. Once Frank hangs up, Carl's men look through wedding announcements to track Frank down.
When Carl tracks him down and arrives at their engagement party to arrest him, Frank admits the truth to Brenda, shows her all his stolen money and asks her to run away with him. Although shocked, she accepts his offer and agrees to meet him two days later at the airport. However, when she arrives as planned, he sees a devastated Brenda being coached by FBI agents, who have surrounded the airport. Realizing that Carl has convinced her to turn against him. When Frank doesn't appear, Carl has his men stake out the airport, certain that Frank will attempt to show him up somehow, and try to escape by plane.
Frank puts a new plan into effect, where he claims that he works for Pan Am, and is recruiting stewardesses to travel to Europe. The girls he chooses work as "eye candy", and Frank manages to walk right past Carl's men, distracting them with a decoy in the unloading zone of the airport. Frank escapes to Europe.
A year-and-a-half later in 1967, Carl angrily tells his boss that Frank has been forging checks all over the Eastern Hemisphere. Only this time, the checks are the real thing. Arguing that Frank is out of control, he requests permission to track him down in Europe. When his boss denies him permission, Carl takes one of Frank's bogus checks to professional printers who suggest it can have been printed in only a handful of European countries. Remembering from an interview with Franks mother Paula that she was born in France, Carl travels to her birthplace of Montrichard and he finds Frank there, on Christmas Eve, inside a massive printing factory. Carl tells Frank that the French police outside will kill him if he doesn't surrender quietly. Frank assumes he is joking at first, but Carl vows that he is not lying. Frank handcuffs himself and Carl takes him outside, where, seeing no police, he compliments Carl on his ability to fool him. Almost immediately, however, the French police arrive and escort Frank to prison. The French police take Frank away, with Carl promising to have Frank extradited back to the USA. After two years, Frank is released into Carl's custody.
Later on Christmas Eve 1969, on the plane extraditing Frank to the United States, Carl informs him that his father had died accidentally the previous year. Devastated, Frank escapes from the plane in incredible fashion, and tracks down where his mother lives. Here he finds his mother with her second husband, as well as a young girl who Frank realizes is his half-sister. Before he can even speak to his mother, however, a posse of police arrive in pursuit and Frank surrenders (it is never explained if Frank's own mother called the police on him or if it was just a coincidence that they showed up at her house).
Frank is tried, convicted, and given a 12-year prison sentence for check forgery, embezzlement, among many other charges, and sent to a maximum security Federal prison in Atlanta. During the next four years, Frank receives regular visits from Carl. During one of these visits, Frank easily deduces the identity of a forger by glancing at a check that Carl shows him. More visits from Carl has Frank cooperating with him in identifying other check forgers.
In 1974, an impressed Carl arranges for Frank to be allowed to serve out the remainder of his sentence working for the check fraud department of the FBI under Carl's custody. Although Frank is out of prison, he is chained to his desk-job and misses the thrill of his old life and even attempts to pose as an airline pilot once again. Just as he tries to run again, Carl meets him at the airport. Carl allows him to go free, predicting that Frank will return to work on Monday since there is no one chasing him.
Back in the office on Monday morning, Carl is nervous when Frank doesn't appear for work on time. He is afraid that he has run away and ruined both their lives. But Frank soon shows up and asks Carl about their next case. Bristling, Carl demands to know how Frank cheated on the Bar Exam in Louisiana, to which Frank replies that he didn't: he had studied for only two weeks and genuinely passed the exam. Astounded, Carl asks him "Is that the truth, Frank?" to which Frank merely smiles. Carl smiles back and the two continue to their investigation work together.
Lastly, it is revealed through scrolling text that "Frank has been happily married for 26 years" had three sons, lives in the Midwest with his family, is still good friends with Carl, caught some of the world's most elusive money forgers and gets millions of dollars each year because of his work creating unforgeable checks.