The film begins with Chorus, in this case a person in modern dress, introducing the subject of the play. He is walking through an empty film studio and ends his monologue by opening the doors to begin the main action. Chorus reappears several times during the film, his speeches helping to explain and progress the action.
The following act divisions reflect the original play, not the film.
Early 15th century in England: The Bishop of Ely and the Archbishop of Canterbury conspire to distract young King Henry V from passing a decree that might confiscate property from the church. They agree to talk him into invading France. Canterbury appears in the throne room and explains to the King's advisers that Henry is rightful heir to the throne of France on the grounds that the Salic law in France unjustly bars his claim to the throne and should be disregarded. Supported by the noblemen Exeter and Westmoreland, the clergymen manage to persuade Henry to declare war on France if his claim on the French crown is denied.
Henry calls in Mountjoy, a representative of the Dauphin. The Dauphin's condescending response takes the form of the delivery of a chest of tennis balls. Exeter, who opens the chest, is appalled, but Henry at first takes the insult calmly. He goes on to state his determination to attack France, dismisses the ambassador and starts to plan his campaign.
Henry tricks three high-ranked traitors into pronouncing their own sentence by asking advice on the case of a man who shouted insults at him in the street. When they recommend that he show no mercy to this minor offender, the King reveals his knowledge of their own sedition; they draw their daggers, but are quickly subdued by Henry's loyal nobles. Exeter arrests them for high treason and Henry orders their execution before crossing the English Channel.
Meanwhile in France, Charles VI, the King of France and his noblemen discuss King Henry's threats. The Dauphin (portrayed as something of a playboy) does not fear Henry, but Charles and the Constable of France are worried because of Henry's martial ancestors and their previous English invasions. Exeter arrives in full armor. He informs them that Henry demands the French crown and is prepared to take it by force if it is withheld, and delivers an insulting message to the Dauphin. King Charles tells Exeter he will give him a reply the following day.
King Henry delivers a morale-boosting speech to his troops and attacks the walled city of Harfleur. When the Dauphin fails to relieve the city in time, the governor surrenders in return for Henry's promise to do Harfleur's population no harm. Henry orders Exeter to repair its fortifications.
Katharine asks her lady-in-waiting Alice to teach her some basics in English. Correct English pronunciation is very hard for her to learn but she is determined to accomplish it, even though some words sound un-ladylike to her. In a silent moment, Katharine watches her father and his courtiers and notes how worried they appear. King Charles finally orders his nobles to engage Henry's troops, halt their advance, and bring Henry back a prisoner.
The English troops struggle toward Calais through foul weather and sickness; Bardolph is hanged for looting a church. The French ambassador Mountjoy arrives and demands Henry pay a ransom for his person or place himself and his entire army at risk. Henry refuses, replying that even his reduced and sickly army is sufficient to resist a French attack.
In the boisterous French camp the night before the battle, the French nobility wait impatiently for the morning, and it is clear that the Dauphin is not popular with the other nobles. In the more sober and silent English camp, following a brief meeting with his brothers, Gloucester and Bedford, together with Sir Thomas Erpingham, Henry decides to look into the state of his troops and wanders his camp in disguise. He meets Pistol, who fails to recognize him. Soon afterwards, he encounters a small group of soldiers, including Bates and Williams, with whom he debates his own culpability for any deaths to follow. He and Williams almost come to blows, and they agree to duel the day after, should they survive. When Williams and his friends leave the King alone, Henry breaks into a monologue about his burdens and prays to God for help.
Next morning, the English Army is outnumbered five to one. Henry encourages his troops with his St. Crispin's Day Speech and responds angrily when Mountjoy renews the Dauphin's offer of ransom. The battle begins with the charge of the French cavalry, but the English archery and countercharge cut down a large part of the advancing army before it ever reaches their lines. When the Constable of France is killed, the dismayed French leaders realize the battle is lost and become desperate. Some of them manage to get behind enemy lines and, deprived of any hope to turn the battle, break the code of chivalry by murdering the young and defenseless English pages and setting fire to the English tents. Henry and his officer Fluellen come upon the carnage and are still appalled when Mountjoy delivers the French surrender.
Henry returns Williams' glove, this time out of disguise, and William is shocked to learn that the man he was arguing with the night before was King Henry himself.
The act ends with a four-minute long tracking shot, as Non nobis is sung and the dead and wounded are carried off the field.
Finally negotiations are made for Henry to be named king of both England and France. He has a brief romantic interlude with Katharine while the French and English royal delegations negotiate the Treaty of Troyes. The film ends with Chorus detailing the history after the events of the film, culminating in the loss of the French throne by Henry VI.