The Sandlot is a nostalgic, coming-of-age story that follows a group of young boys and their summer misadventures in the early 1960s. The story begins when Scotty Smalls, a shy and awkward new kid, moves to a suburban Los Angeles neighborhood with his mom and new stepfather. With no friends and no skill in baseball, he is encouraged to venture out and meet the local boys who play every day on a run-down baseball diamond they call the Sandlot. 

Reluctantly, Smalls attempts to join the game but embarrasses himself completely when he can't catch a simple fly ball, causing the other kids to ridicule him. However, the team's kindhearted star player, Benny "The Jet" Rodriguez, takes Smalls under his wing, teaching him the fundamentals of the game. With Benny's guidance, Smalls is welcomed into the fold, joining the rowdy group of nine boys who spend their endless summer days playing baseball. 

The summer is filled with classic childhood antics and unforgettable moments. There's a rivalry with a snobby, organized Little League team, a memorable scene at the local pool involving a scheme by the nerdy Squints to get a kiss from the beautiful lifeguard, and a hilarious misadventure at a carnival involving chewing tobacco. 

The main conflict of the film, however, comes when the team's only baseball is destroyed. Eager to please his new friends and save the day, Smalls "borrows" a baseball from his stepfather's trophy room, completely unaware of its value. Inevitably, he hits a home run that sends the ball flying over the back fence and into the junkyard of their reclusive neighbor, Mr. Mertle. The boys are horrified when Smalls reveals the ball was signed by none other than baseball legend Babe Ruth. 

With the fate of Smalls' relationship with his strict stepfather hanging in the balance, the boys hatch a series of increasingly ridiculous plans to retrieve the ball from the junkyard. The obstacle they face is "The Beast," a monstrous, slobbering English Mastiff that they believe is a terrifying legend. After several failed attempts involving a homemade mechanical contraption, Benny decides to go in after the ball himself. He successfully retrieves it but is then chased by the dog, a wild and intense chase that takes them all over the neighborhood. 

The climax reveals that the menacing Beast is actually a friendly dog named Hercules, whose chain had simply snapped. When the boys meet his owner, the initially intimidating Mr. Mertle, they learn he was a former baseball player who once played with Babe Ruth. In exchange for the bat and with an agreement that the boys visit him regularly to talk baseball, Mr. Mertle gives Smalls a new ball, signed by the entire 1927 New York Yankees team. 

The movie ends with a glimpse into the future, as an adult Smalls narrates what happened to each member of the Sandlot gang. The summer, and the challenges they faced together, cemented their friendship forever and became the stuff of legend.