It is based on the true story of Phiona Mutesi (Nalwanga). Phiona is a pre-teen girl living in Katwe, a desperately poor slum neighborhood in Kampala, Uganda. Into this slum comes Robert Katende (Oyelowo), who works for a Catholic mission. Katende has started a chess club as an activity for the youth of the neighborhood. Phiona tries to enter the club, but the other kids make fun of her because she smells bad—Phiona and her family live in a shack without running water. Phiona cleans up, enters the club, and learns the game. Soon she is beating all the other kids in Katende's club. Katende realizes that Phiona is a chess prodigy.
Meanwhile, Phiona's mother Harriet (Nyong'o), is occupied with the desperate struggle of day-to-day life in the slums of Katwe, raising four children as a single mother after the death of her husband. The family is eking out a hand-to-mouth living by selling ears of corn in the streets, and Harriet has other problems, like her eldest daughter Night and Night's habit of riding around on a motorcycle with a thoughtless young man named Theo. The pressures of their life in poverty and Phiona's desperation to escape life in Katwe bring tension to the family.
- Based on a True Story: A quite accurate account of the life of Phiona Mutesi and how she rose to chess stardom.
- Big Game: The film ends with Phiona winning the Ugandan chess championship.
- Call-Back: When Phiona is first learning the rules of chess, another student at Robert's club explains that in chess, a lowly pawn can become a queen. This is symbolic of Phiona rising from the slums to chess stardom, but it also pays off in the Big Game at the end when Phiona wins the Ugandan chess championship by queening a pawn.
- Desk Sweep of Rage: One boy wipes all the chess pieces off the board in a fit of anger after Phiona beats him.
- Disappeared Dad: Phiona's father died when she was a small child.
- The Disease That Shall Not Be Named: The death of Phiona's father is mentioned several times but the movie never says what he died of of. Phiona's father died of AIDS when she was three.
- Earn Your Happy Ending: After all that, after living in a shack and being homeless and living in an abandoned church, Phiona's success at chess earns the family a house.
- Fish out of Water: The kids from Katwe have a little difficulty when they go to an elite private school to play in a chess tournament. One kid gets so scared that he has a panic attack. Another one of Robert's students gets irritated when he tells her that she should use a fork rather than just ripping the chicken up and eating with her hands.
- Flashback: A couple brief ones from Robert's youth. In one he remembers how much he enjoyed beating city boys at chess. In another he remembers meeting his mother for the first time when he was six.
- Fright-Induced Bunkmate: Phiona and the other young Pioneers are all given their own beds while visiting King's College for a tournament, but they all end up huddled together on the floor because they're intimidated by the prospect of playing against "city boys".
- Gray Rain of Depression: In Katwe after Phiona comes home in despair after doing poorly in a chess tournament in Russia. This one is more plot-relevant when it becomes a flash flood that nearly kills Phiona's little brother.
- Horrible Housing: Phiona and her family live in a shack with no running water. Before joining the Young Pioneers, she'd hardly ever taken a bath.
- How We Got Here: The film starts with a brief scene showing Phiona entering the Ugandan chess championship, before jumping back four years to show the beginning of how she learned the game.
- Hypocritical Humor: The arrogant headmaster of the private school only lets the Katwe kids into the chess tournament after Robert browbeats him into it, then automatically assumes that Phiona is the weakest player on Robert's squad. After Phiona goes to Moscow to represent Uganda in a tournament, the headmaster is shown listening on the radio and saying "I always believed in that girl!"
- Never Learned to Read: Phiona was forced to drop out of school at age six and as a consequence can't read. Robert's wife Sara has to teach her to read so she can comprehend the chess books Robert gives her.
- Opposing Sports Team: Averted in some instances, but a couple of kids are obnoxious to Phiona. The champion of the private school sneers at Phiona that "this isn't the ghetto", right before Phiona beats him.
- Real-Person Cameo: Combined with Video Credits. The end credits feature each actor from the film together with the real person that they played.
- Real-Person Epilogue: The film ends with a credits sequence in which each of the major actors appears alongside the real-life person they were playing.
- Stink Snub: When Phiona first tries to join the chess club, the other kids refuse to play against her because she smells due to her house not having running water. Finally, one little girl agrees to play a match if Phiona will go away afterwards.
- Surpassed the Teacher: The exact moment that Robert realizes this comes when he believes that Phiona has made a mistake and failed to respond to his attack. She proceeds to show him an eight-move sequence in which she forks with a bishop and takes Robert's rook. Robert is astonished that she can see eight moves deep.
- Surprise Checkmate: Phiona pulls off a few of these. In one scene Phiona moves her queen to the back row to put her opponent in check. Her opponent takes Phiona's queen with her rook then sniffs "You don't know anything." What her opponent doesn't know is that Phiona sacrificed her queen to force her opponent to move the rook, which cuts off her king's escape; Phiona moves her knight and checkmates her opponent on the next move.
- Team Power Walk: Phiona, Robert, and their entourage as they enter the decisive match of the Ugandan chess championship.
- The Voiceless: The older Canadian girl that never says a word but stares daggers at Phiona throughout their match in Russia. It seems to work in unnerving Phiona, and she loses.
- Wrong Side of the Tracks: Katwe. A desperately poor slum without electricity or running water. In one scene Harriet sells a nice dress, practically the only thing of value she owns, to buy more paraffin. The paraffin is necessary to burn so that Phiona will have light to study her chess books with at night.