Squire Allworthy returns to his estate from London to find an infant abandoned in his chamber. He entrusts the child to the care of his sister and brings the boy, Tom, up as a member of the family alongside his nephew, master Blifil. Tom is as kind and benevolent as Blifil is spiteful and selfish.

Tom’s creditable actions include supporting his friend, Black George Seagrim, the gamekeeper. Tom is popular with Allworthy’s neighbour, Squire Western, and falls in love with his daughter, Sophia.

Tom has a physical relationship with George’s daughter, Molly, and she initially tries to label him as the father of her child.

Blifil’s hatred of Tom means he works to have him thrown out of Allworthy’s house. Black George, tempted beyond his conscience, takes Tom’s money.

Tom wanders the country, considering becoming a soldier. He meets up with Partridge, a former teacher who was believed to be Tom’s father. Tom and Partridge travel amicably together.

Meanwhile, Sophia Western is confined by her father for refusing to marry Blifil.  She escapes, and Tom and Sophia search for each other. Sophia rejects her feelings for Tom when she discovers he has slept with another woman. Tom is indulged and supported in London by a Lady Bellaston. She had promised to help him locate Sophia but really wants Tom for herself.

Sophia’s aunt, Lady Western, is anxious for her to marry the aggressive Lord Fellmar.

Tom is imprisoned for duelling and suspected of incest, but both charges are revealed to be untrue. Allworthy finds out that Tom is his nephew, Bridget’s illegitimate son, and that Blifil has kept the information from him. Blifil organized the imprisonment of Tom.

The charges against Tom are dropped. He and Sophia are married with the blessing of both parents. Blifil is disgraced but remains financially supported by Tom. Sophia and Tom live close to their friends Nightingale and Nancy. Partridge returns to teaching and marries Molly Seagrim.