Rowlet debuted in The Fires of a Fierce Battle!, where he was under the ownership of Hala. After witnessing Lewis defeating Luna in the final round of the Iki Town Festival Tournament, Rowlet takes an interest in the Trainer and later decides to follow him.
When the group were cornered by a group of angry Rattata and Raticate, Rowlet saved them by using Leafage to push back the Mouse Pokémon, although he did not reveal himself to the group at this point.
In the next episode, Rowlet finally decided to make his presence known to Lewis, silently sneaking up on him and challenging him to a battle. Rowlet faced up against Lewis' Aipom and was able to confuse his opponent with his silent movements, although he was eventually defeated by Aipom's Thunderbolt. Rowlet then expressed his desire to travel with Lewis, who asked Hala if that was okay. Hala was more than happy with Rowlet's decision and sent Lewis Rowlet's Poké Ball. Rowlet happily went inside its Poké Ball.
In For the Power of Z!, Rowlet reunited with his former Trainer, who was impressed with how his strength had improved in such a short time.
In the next episode, Rowlet participated in Ilima's trial at Verdant Cavern. He battled against the Totem Gumshoos alongside Aipom. Rowlet put up a good fight, managing to deal severe damage to Gumshoos, he was eventually defeated by a powerful Giga Impact, leaving Aipom to continue the fight alone.
Rowlet was Lewis' first Pokémon in his Grand Trial battle against Hala in The Call of Tapu Koko! He faced off against Hala's Mankey and defeated it with a supereffective Pluck, although it was paralysed by Thunder Punch in the process. Hala then sent out his Makuhita, who proved to be a sturdier opponent than Mankey. Rowlet attempted to strike with Tackle, but Makuhita used Force Palm to counter it. After managing to land a Leafage attack, Rowlet was defeated by a double-powered Smelling Salts.
In A Seafaring Trial!, Rowlet was Lewis' third and final Pokémon in his battle against the Totem Wishiwashi. Despite maintaining a type advantage, Rowlet's Leafage did little damage to Wishiwashi due to its massive bulk. Eventually, Rowlet was slammed into the water by a powerful Aqua Tail. Activating his Overgrow Ability as a result of all the damage he had taken, Rowlet was able to deal massive damage to Wishiwashi with a powered-up Leafage. Wishiwashi struck back with a Double-Edge, sending Rowlet flying into his Trainer's arms, although the damage Wishiwashi had taken caused it to revert to its Solo Form. Wishiwashi called for its ally Alomomola to help it out. Alomomola attempted to use Heal Pulse on Wishiwashi, but Lewis commanded Rowlet to intercept the move, thereby healing Rowlet instead of Wishiwashi. With its health fully restored, Rowlet defeated Alomolola with Leafage and then struck Wishiwashi with a powerful Tackle, knocking it out and earning Lewis a Waterium Z.
Rowlet participated in the Battle Royale tournament in A Royal Rumble!, where he was used in the second round. While the start of the battle had occurred off-screen, Rowlet was shown defeating a Sneasal, leaving him the last Pokémon standing and allowing Lewis to move on to the final round.
In Shop Till You Drop!, Rowlet was used in a three-on-three battle against Kiawe. Facing off against Kiawe's Growlithe, Rowlet's Leafage was quickly incinerated by Flamethrower. A clash between Tackle and Flame Charge resulted in Rowlet being overpowered and knocked out.
In Aiming for Greater Heights!, Rowlet was sent out by Lewis as his partner in the Vow Tower competition, where Trainers and their Flying-type Pokémon compete in challenges in order to reach the top of the Vow Tower. Lewis and Rowlet became the first pair to reach the top of the tower and were given a Flyinium Z as their reward. Just then, a Team Skull grunt and his Staraptor arrived and attempted to steal the Z-Crystal. Lewis and Rowlet battled them, with Rowlet evolving into Dartrix during the battle. With its newly learned Leaf Blade and increased speed, Dartrix was able to outmaneuver Staraptor and finally defeated it when Lewis and Dartrix performed Supersonic Skystrike for the first time.
Dartrix was Lewis' final Pokémon used in his battle against the Totem Lurantis in It's a Jungle in There! Despite putting up a good fight, Dartrix was quickly defeated by Lurantis' Solar Blade, resulting in Lewis' loss. After training with Lewis, Dartrix went up against the Totem Lurantis once again as Lewis' first Pokémon. Despite his use of Leafage to block out the sun, preventing Lurantis from charging its Solar Blade as quickly, Dartrix was still defeated, although it had managed to get a few good hits in beforehand.
In a Rock Solid Grand Trial!, Lewis used Dartrix in his Grand Trial battle against Olivia. Sent out to face Olivia's Boldore, Dartrix quickly became overwhelmed by Boldore's powerful Rock Slide, forcing Lewis to use Bloom Doom in order to defeat it. The use of the Z-Move, combined with the damage he had taken from Boldore, wore Dartrix out, allowing Olivia's Lycanroc to easily defeat it with Accelerock.
Dartrix was used to battle several of Novu's Rusted Pokémon during the Rust arc.
Dartrix was Lewis' first Pokémon used in his battle against Hau in Clash on the Cape! He faced off against Hau's Litten and defeated it easily, despite the type disadvantage. He was also used in Lewis' battle against Molayne in Trial for the Trial!, where he was defeated by Skarmory.
In Setting the Trap!, Lewis sent out Dartrix to battle a wild Turtonator he wished to catch. Dartrix struck hard with Leaf Blade, but suffered severe damage as a result of Turtonator's Shell Trap, leaving himself open for Turtonator to defeat him with Flamethrower.
Dartrix was used in Team Skull Takeover! to fight several Team Skull grunts who had stolen Nebby. Despite putting up a good fight, Dartrix soon became overwhelmed by the number of opponents and was knocked out by a Poison Fang from Golbat.
In Night Out with Nanu!, Lewis used Dartrix to battle against Nanu's Sableye in their Grand Trial battle. Dartrix was able to knock out Sableye after redirecting its Shadow Ball with Leafage, although it fell to Krookodile despite the type advantage.
Dartrix was again used by Lewis in his rematch with Nanu in Revenge - Best Served Hot! He battled Sableye and defeated it once again. Dartrix was then sent out to battle Nanu's Alolan Persian and, despite dealing major damage with its newly-learned Brave Bird, was defeated by Persian's Power Gem.
Lewis sent out Dartrix to battle a group of mercenaries in A Resolution for Zygarde! It attempted to protect the entrance to Resolution Cave from the mercenaries, but was thrown off the cliff and into Poni Meadow. Refusing to back down, Dartrix evolved into Decidueye and continued the battle, using its new Spirit Shackle to prevent the mercenaries from recalling their Pokémon. As the mercenaries attempted to flee, Zygarde finally awoke and changed into its 50% Forme, sending the mercenaries flying with its Thousand Arrows. After this, it was discovered that the mercenaries were members of the Aether Foundation.
As a Rowlet, Dartrix was shown to be a very friendly Pokémon, immediately making friends with Lewis and Aipom. He was also shown to love battling, to the point where he followed Lewis in order to fight powerful opponents. Rowlet would often pop out of his Poké Ball whenever he sensed a strong opponent, highlighting his love for battle, a trait he kept when he evolved into Dartrix.
Dartrix is often shown to become disappointed in himself after losing a battle. Despite this, he uses his losses to help him to grow stronger, as shown in his focus during training after losing to the Totem Lurantis in It's a Jungle in There!
As a Dartrix has grown more serious and will often perch away from the rest of the group in order to prune himself. Despite this new seriousness, Dartrix is still willing to play with the other Pokémon, as seen in Dazzling the Ocean Depths!
Upon evolving into Decidueye, it kept its serious and distant nature, although it maintained an undeterred loyalty to Lewis. Decidueye now stops coming out of his Poké Ball on his own, showing a new maturity. He is shown to be proud of his power, although is respectful to its opponents, as seen in his battle against the mercenaries in A Resolution for Zygarde!