The film begins with a silent film sequence, with subtitles, during which Squire Allworthy returns to his estate after a lengthy stay in London and discovers a baby in his bed. Thinking that one of his maids, Jenny Jones, and his barber, Mr. Partridge, conceived the illegitimate baby out of lust, the squire banishes them. He names the infant Tom Jones and chooses to raise him as if he were his own son; Tom grows up loving him like a father.
Tom becomes a lively young man whose good looks and kind heart make him very popular with girls and women. He truly loves only the gentle Sophie Western (Sophia "Sophy" in the novel), daughter of a neighbor, who returns his passion. Tom is stigmatized as a "bastard" and cannot wed a young lady of her class. Sophie, too, must hide her feelings while her aunt and her father, Squire Western, try to coerce her to marry someone they think more suitable, the nephew of Squire Allworthy.
This young man is Mr. Blifil, the son of Squire Allworthy's widowed sister Bridget. Although of legitimate birth and appropriate class, he is an ill-natured prig with plenty of hypocritical 'virtue.' When Bridget dies unexpectedly, Blifil intercepts a letter, which his mother intended for his uncle's eyes only. The letter's contents are not revealed until late in the film. But after his mother's funeral, Blifil and his two tutors, Mr. Thwackum and Mr. Square (who also tutored Tom), join forces to convince the squire that Tom is a villain. Allworthy gives Tom a small cash legacy and sorrowfully sends him out into the world to seek his fortune.
In his odyssey on the roads, Tom is knocked unconscious while defending the good name of his beloved Sophie and robbed of his small legacy. He also flees from a jealous Irishman who falsely accuses him of having an affair with his wife, Sophie's cousin; engages in deadly sword fights, rescues a Mrs. Waters from a British army officer, and later beds her. Before that occurs, Tom and Mrs. Waters have a celebrated scene in which they wordlessly and voraciously consume a hearty meal while gazing lustfully at each other. Later, Tom meets Partridge, his alleged biological father, and engages him as a servant.
Meanwhile, Sophie runs away from home soon after Tom is banished, in order to escape the attentions of the loathed Blifil. After narrowly missing each other at the Upton Inn, Tom and Sophie arrive separately in London. There, Tom attracts the attention of Lady Bellaston, a noblewoman over 40 years of age who is attracted to the "pretty boy". She is rich, beautiful, and completely amoral. She invites Tom to a masked ball at Vauxhall Gardens and seduces him. Tom goes to her bed willingly and is generously rewarded for his services with a suit of fine clothes.
Lady Bellaston tries to force Sophia into marriage to a lord by having her raped by him, so that she can have Jones to herself. Sophia is saved when her father bursts in.
Hoping to disentangle himself from the affair with Lady Bellaston, Tom writes to her proposing marriage, knowing she will reject the proposal and him. She does, but she also shows the proposal letter to Sophia, who writes to Tom breaking off all contact with him.
Tom visits Sophia's cousin, Mrs. Fitzpatrick, to ask her to speak on his behalf to Sophia. Mr. Fitzpatrick sees him leaving and, assuming his earlier suspicions of an affair between Tom and Mrs. Fitzpatrick were correct, engages him in a duel. The sword fight ends in the wounding of Mr. Fitzpatrick and the crowd thinks Tom was robbing him. Tom ends up at Tyburn Gaol, sentenced to hang for robbery and murder.
Partidge runs into Mrs. Waters and recognises her as the former Jenny Jones, Tom's alleged mother. He tells her that the man she 'met' is her alleged son and that he is awaiting execution. Squire Allworthy is troubled to hear that Tom has apparently been involved in incest. However, Mrs. Waters visits Mr. Allworthy and tells him the truth: Tom is not Jenny Jones's child, but his sister Bridget's illegitimate son and thus Allworthy's nephew. Allworthy also learns of the mysterious letter that was supposed to reveal this. Since Blifil knew of the letter, concealed it, and tried to destroy his half-brother, Allworthy disinherits him.
Allworthy also learns that Mr. Fitzpatrick has recovered and withdrawn the charge against Tom. Allworthy uses this knowledge to get Tom a pardon, but it arrives too late: Tom has been conveyed to the gallows; the noose is around his neck. Squire Western, who has been apprised of Tom's new status as Allworthy's only heir, cuts him down as he begins to hang and takes him to Sophie.
Tom has permission to court Sophie, and all ends well with Tom embracing Sophie with both Squire Western's and his uncle's blessings. Squire Western predicts a child will be born "tomorrow and ninemonth".
Tom "lives to love another day".
