Kahili and her Toucannon, nicknamed Touckey, are ambushed by a group of reporters, who start asking her questions about her recent losing streak, her secret return to Alola, and her rumored retirement. Touckey is able to repel the reporters with a loud yell, giving Kahili the chance to escape from them. As she and her partner Pokémon flee through a forest, Kahili wonders if she really should quit golfing. Nearby, Ash and Kiawe are playing baseball outside the Pokémon School, while the rest of the class and their Pokémon watch. Ash is at the bat and swears to make a home run, while Kiawe plans to stop him. Kiawe pitches the ball, but Ash accidentally hits a foul ball. Just then, Kahili emerges from the woods as the ball heads towards her. Upon spotting it, she swiftly pulls out a golf club from her bag and hits the ball back like a golf ball. It is sent bouncing inside the school bell, from which it is kicked back down to the schoolyard by Komala and caught by Turtonator, amazing everyone.
As everyone goes to greet Kahili, they are briefly stopped by Touckey, who stands in front of her defensively, but Kahili assures it that it is okay before asking where she is. Professor Kukui explains that she is at the Pokémon School and asks if she is Kahili. When she confirms this, Mallow and Sophocles immediately become excited, having heard of her before. Ash is intrigued by Kahili's golf club, and the whole class asks to try them out as well. Touckey presents a golf club to each of the students, which they hold and examine. When Sophocles asks Kahili if she could play some Pokémon Golf with them and Ash asks what Pokémon Golf is, Sophocles explains that it is golf played together by people and Pokémon. The whole class joins in this request, but Kahili is uncertain. However, after an encouraging push from Touckey, she agrees to take everyone to play Pokémon Golf. As a result, Professor Kukui changes the rest of the day's classes to Pokémon Golf.
Later, everyone arrives at a Pokémon Golf course. Kahili takes them to the teeing ground of the first hole and explains the rules to them: the ball has to be hit from the tee to the cup at the putting green, where a flag marks the cup's location, and the one who gets the ball to the cup with the fewest swings wins. However, the most important rule is the cooperation between Pokémon and their Trainers. Unexpectedly, an old man shows up, introducing himself as the master caddy, a legendary Pokémon Golfer with 40 years of experience. However, no one in the class, nor Kahili, has any idea who he is. He offers to assist everyone with his 50 years of experience, promptly ignoring Rotom's comment about the sudden increase in the number of years.
Kahili makes the first swing, with Touckey using Tailwind to give her ball more speed. To the class's amazement and even Kahili's own surprise, the ball goes straight into the cup, resulting in a hole-in-one. The master caddy, now boasting with his 60 years of experience, claims that he was the first one to think of using Tailwind at the first hole, and everyone has been copying him ever since, much to Touckey's annoyance. The class then begins taking turns at hitting a ball, with Ash taking the lead. Touckey pushes Kahili into offering Ash some advice, and she shows him how to properly swing the club. Ash successfully hits his ball hard, but he accidentally sends it flying high into the air rather than towards the cup. Pikachu rushes ahead, and Ash, remembering the cooperation part of the sport, has Pikachu use Iron Tail to successfully launch the ball towards the putting green. Next, Mallow hits her ball, but it rolls away from the hole. At that moment, Shaymin pops out of some nearby bushes and knocks the ball into the cup. The master caddy boasts that he has seen this sort of miracle many times during his 70-year-long career, but he is cut off by an annoyed Touckey chomping down on his head.
At the third hole, Kiawe makes a similar chant as he does while using Inferno Overdrive as he prepares to swing, but then retreats at the last second and reveals he wants Marowak use Shadow Bone to hit the ball instead. However, Marowak hits the ball too hard, and it disappears into the sky. Kahili says it was still a good try and encourages them to try again. This time, Marowak hits the ball with its bone without using a move, sending it straight to the putting green, much to Kiawe and Marowak's joy. At the fourth hole, Lillie tries to avoid hitting the Alolan Exeggutor standing around the course, but her first few swings fail to even hit the ball. After Kahili tells her to just take a deep breath and relax, she makes a successfully swing without hitting any of the Exeggutor, much to her delight. The master caddy says that relaxation through deep breaths was something he has told people every day throughout his 80-year career, prompting Touckey to once again chomp down on his head.
At the fifth hole, Sophocles has to putt his ball through an uneven green with a Spinarak and several Alolan Diglett acting as obstacles. He starts running some calculations, but Togedemaru promptly puts the ball on the move without waiting, successfully avoiding the obstacles and putting the ball into the cup. The master caddy says his 90 years of experience could've offered a better way, doing his best to ignore Touckey chomping down on him. At the sixth hole, Lana has her Brionne create a bunch of balloons. The Pop Star Pokémon does as told and also starts singing, with the class's Pokémon and the nearby wild Pokémon all joining in on the singing and dancing. To Kahili's surprise, even Touckey joins in after being asked by Pikachu, saying that she hasn't seen it acting like this in a long time. When Kukui points out that Touckey must be happy to see her having so much fun, Kahili realizes that Touckey must've wanted her to come play Pokémon Golf with these children to cheer her up. One of Brionne's balloons lifts up Lana's golf ball, and she hits it right next to the cup in the putting green.
Through the following holes, the class continues to make progress, with Kiawe swinging his ball over a group of Exeggutor, Lana using a combination of Brionne's Surf and Sandy's Tackle to move the ball, and Lillie using Snowy's Powder Snow to create herself an icy slope to move her ball close to the cup without needing to try too hard. Impressed by everyone's performance, the master caddy offers to take them to the "Tenth Hole of Doom", which turns out to be located in a windy canyon, with the putting green standing high above them on a small platform. Any ball that fails to go into the cup here will fall into the valley below, making this course particularly hard. The master caddy offers to demonstrate, pulling out a Poké Ball from his golf club bag and sending out a Krabby to be used as his club, much to everyone's bafflement. The odd strategy appears to work, but just then, the wind picks up, pushing the flying ball down into the valley. Rotom realizes that the master caddy just showed them an example of how to fail, which he confirms to be true, saying that even the best of players can end up like this after just one misstep. He then challenges Kahili to do this challenge, as she's a pro golfer. Despite Rotom saying that the odds of getting the ball into the tenth hole is 0.00001 percent, Kahili accepts the challenge.
As Kahili and Touckey prepare for their swing, Ash and his classmates give encouragements to her from the background, and she thanks them all for their moral support. Filled with confidence, she strikes the ball as hard as she can, and Touckey uses Tailwind to speed the ball toward the green. However, the wind in the canyon whips up again, and the ball starts falling back. Not hesitating for a second, Kahili picks up Touckey by its legs and aims it at the falling ball. Touckey's beak starts heating up, and Kahili commands it to use Beak Blast, firing a massive beam that sends the ball hurtling back towards the green, successfully landing it in the cup. As everyone else celebrates Kahili's success, the master caddy walks away, saying to himself that there is nothing left for him to teach her at this hole, and that he'll be waiting for her at the "Eleventh Hole of Doom".
Later, Ash and his classmates are all following Kahili's newest competition on television from their respective homes. She successfully pulls off her final putt and wins the competition, much to everyone's delight. She thanks everyone at the Pokémon School for reminding her of how fun it was playing when she was just starting out as well, happily holding up her new trophy.