With its opening, Dear John debuted as the No. 1 movie with $32.4 million, knocking off Avatar after seven weekends in first place. The film has a record opening for Super Bowl weekend, topping the $31.1 million debut for Hannah Montana & Miley Cyrus: Best of Both Worlds Concert in 2008. It is also the best debut for a film based on a Nicholas Sparks novel.
The movie opens with John Tyree, a young soldier from the Army Special Forces, lying on the ground in his army gear with gunshot wounds. Coins begin to fall over him as he remembers a childhood trip to the U.S. Coin mint. He goes on to state that he is a coin in the United States of America's army, and that the last thing he thought about before he blacked out, was you.
In 2001, college student Savannah Lynn Curtis (Amanda Seyfried) is on spring break when she meets John Tyree (Channing Tatum), a young soldier on leave from the Army Special Forces. In a matter of days, Savannah and John fall in love. John meets Savannah's family as well as her neighbor Tim and Tim's autistic son who looks up to Savannah, Alan. Savannah meets John's father, who is only interested in his coin collection, but still befriends her.
John explains to Savannah that his father has always been obsessed with coins, and has not been much of a father to John since John's mother left. Savannah mentions John's father may, like Alan, have autism, causing John to become upset and believe Savannah is calling his father retarded. He also gets into a fight with Savannah's rich neighbor and accidentally punches Tim in the process. John apologizes to Tim the next day and leaves Savannah a note, seeking her forgiveness before his leave comes to an end. Savannah gets the note, and they spend one last day together. John returns to the army and he and Savannah begin a long distance relationship through handwritten letters. John believes that year will be his final year of enlistment, but, following the September 11 attacks, is torn between returning home and his sense of duty. He is given eighteen hours off, which he spends with Savannah and her family as well as with his father. He asks Savannah for her opinion on whether or not he should reenlist, and she tells him to do what he feels is right. Like the rest of the soldiers in his unit, John chooses to reenlist.
Over the next seven years, John faces increasingly dangerous missions and begins to live almost entirely for Savannah's letters. However, John and Savannah find themselves drifting apart. Finally, Savannah, sad but resigned, sends John a Dear John letter, informing him that she has become engaged to someone else. John is deeply depressed and frustrated and believes she is engaged to her rich neighbor. On a mission, he enters a dangerous area and is shot several times by an enemy. His captain suggests that John go home and spend time with his father, but John, still upset about Savannah, chooses to reenlist again. He decides that he will make a career of the Army and stay enlisted for as long as possible. He is informed after another mission that he is being sent home, because his father has had a stroke. He spends the last few days of his father's life by his side, and writes him a letter.
His father has difficulty opening it, so John reads it to him. It is then that the viewers find out that when John's speech at the beginning of the film addressed his father, not Savannah. He and his father connect in a tearful moment, and his father passes. John decides to go see Savannah, and discovers she married Tim, not her rich friend. Savannah tells him Tim has cancer, and is not allowed to leave the hospital. She says that the only way he can come home is by having a operation that they cannot afford. John visits Tim in the hospital and leaves Savannah. John then sells his father's coin collection and donates the money anonymously to finance Tim's operation so that Tim may spend his last moments with his family. In the last scene of the film, John sees Savannah on the street and they embrace.