Sawyer Treecko as his starter Pokémon from Professor Birch. They started the journey together and encountered a Taillow. To defeat it, Sawyer thought of some tactics, which Treecko utilized and managed to defeat Taillow thoroughly.
Treecko was battling Clemont and his Luxray in a battle. Luxray used Wild Charge and easily knocked out Treecko. Clemont proposed to Sawyer he could've had Treecko use Razor Leaf somewhat earlier, before Luxray attacked, while Sawyer wrote that in his notebook.
Later it is used in a Double Battle against Ash, teaming up with Sawyer's Bagon. Treecko used Leech Seed on Hawlucha, who dodged the attack. Treecko used Bullet Seed on Frogadier, who dodged the attack. Treecko repeated the attack, but lost to Ash's Frogadier when it used Cut by deflecting its Bullet Seed in mid air and quickly knocks him off in explosion with another Cut.
Treecko also reveals to love Serena's home made Poke Puffs after Sawyer tasted Serena's homemade cakes and became impressed to her baking skills. When Sawyer lost his notebook and the heroes found out Team Rocket took the notebook, Sawyer had Treecko use Bullet Seed and Pikachu using Thunderbolt to retaliate against Pumpkaboo's Shadow Ball and Inkay's Psybeam, allowing Pikachu to blast Team Rocket off with another Thunderbolt. Treecko was later used in a triple battle against Ash. Treecko, despite getting hit by Ash's Frogadier, retaliated with Bullet Seed, hitting Frogadier, then used Agility. Frogadier hit it with Water Pulse, making Treecko furious and is not giving up the fight. Treecko angrily roars to evolve into a Grovyle. 
Ash told Sawyer the evolution was a success, since Sawyer shared his feelings with Grovyle through his passion in battling. Grovyle tests its newly Leaf Blade and becomes confident to face Frogadier who uses multiple illusions using Double Team as Grovyle make a strike using Leaf Blade but it slashed the illusion and the real Frogadier used Aerial Ace, hitting Grovyle, who repeated the attack and clashed with Frogadier's Cut attack. Grovyle used Bullet Seed, which got countered by Frogadier's Water Pulse. Grovyle proceeded to finish the battle with Leaf Blade, but it attacked an illusion, while the real Frogadier who is in mid air from behind and used Water Pulse to defeat Grovyle.
After the heroes departed from Anistar City, they found Sawyer and Grovyle, who were chasing some Dodrio for Sawyer to catch. Upon finding out Squishy had been captured by some men in red, Sawyer had Grovyle use Leaf Storm, which hit Celosia's Drapion, along with Pikachu's Thunderbolt, causing Drapion to drop Squishy. Later, Ash teamed up with Sawyer, having his Pikachu use Thunderbolt and Sawyer having Grovyle use Leaf Blade on Drapion's Pin Missile.
For his final Pokémon to battle with, Sawyer sent Sceptile against Ash's Greninja. Sawyer was impressed Ash also managed to evolve his Greninja. Sceptile started the battle with Cut, but Greninja dodged the attack. Knowing type disadvantage meant little in a battle against Ash, Sawyer had Sceptile use Leaf Blade to block Greninja's Aerial Ace. Sceptile managed to hit Greninja with Dragon Pulse and Leaf Storm. Sceptile managed to bash Greninja to the ground, who synced his mind with Ash, transforming himself. This surprised Sawyer, since Greninja was too quick for Sceptile, who was defeated by Greninja's Aerial Ace.
Sceptile was sent as Sawyer's last Pokémon to use in a three-on-three battle against Ash and his Greninja. Greninja and Sceptile clashed with Aerial Ace and Leaf Blade attacks, then collided with Water Shuriken and Bullet Seed attacks. Sceptile tried to use Leaf Blade, but Greninja used Double Team, dodging the attacks. Greninja attempted to use Cut, but Sceptile elegantly dodged the attack and hit it with Leaf Storm. Greninja attempted to hit with Aerial Ace, but was slammed away by Sceptile's tail. Ash tried to get Greninja to activate its power, but this time, it failed due to Ash and Greninja not being in complete sync with each other. Despite this, Sceptile managed to defeat Greninja with Leaf Storm and Leaf Blade and win the battle for Sawyer. This made Sawyer and Sceptile happy they managed to defeat Ash and Greninja for the first time ever.
After Sawyer's Slurpuff got defeated, he sent Sceptile to battle Tierno's Blastoise. Blastoise used Ice Beam, which got countered by Sceptile's Leaf Storm. Blastoise attempted to launch Hydro Cannon, but Sceptile avoided the attack and slashed it with a super-effective Leaf Blade. To finish it off, Blastoise used Skull Bash, but was thrown in the air by Sceptile's Frenzy Plant. Before it was knocked out, Blastoise used Rain Dance to help Raichu have the advantage against Sceptile. Raichu used Thunder, which, due to the rain caused by Tierno's Blastoise's Rain Dance, made it an unmissable move. However, Sawyer Mega Evolved his Sceptile, who, despite being electrocuted, took no damage, due to Mega Sceptile's Lightning Rod ability. Raichu attempted to use Focus Blast, but was defeated by Mega Sceptile's Dragon Claw attack.
As his last Pokémon during the semi-finals, Sawyer sent Sceptile to battle Ash's Pikachu. Pikachu used Quick Attack, but Sceptile's Leaf Storm blew him away, who used Thunderbolt to break through the attack and hit the latter. Sceptile used Leaf Blade to negate Pikachu Iron Tail and defeated him with Frenzy Plant. Ash sent Greninja as his last Pokémon, who started off with Water Shuriken. Sceptile sliced the attack with Dragon Claw and used Frenzy Plant to banish Greninja's Double Team illusions. Greninja came closer to Sceptile and used Cut to clash with its Leaf Blade. Ash synchronized with Greninja, who transformed itself, while Sawyer Mega Evolved his Sceptile. Ash-Greninja used Cut to slice through Frenzy Plant roots and fired Water Shuriken, which got, once again, stopped by Mega Sceptile's Dragon Claw. However, Mega Sceptile got punched by Ash-Greninja's super-effective Aerial Ace. Mega Sceptile retaliated with Leaf Storm and knocked Ash-Greninja away. Using Leaf Blade, Mega Sceptile clashed with Ash-Greninja's Cut before repeating Leaf Storm to blow Ash-Greninja away. Ash-Greninja used Cut to slice through Frenzy Plant, though it did have trouble coming closer to Mega Sceptile to attack. After dodging another Frenzy Plant and used Cut on it again, Ash-Greninja cornered Mega Sceptile with Double Team. Ash-Greninja conjured a giant Water Shuriken, which Mega Sceptile tried to stop with Leaf Storm. However, it failed and Mega Sceptile, who turned back into Sceptile, fainted from the attack, eliminating Sawyer from the Conference.
Sceptile stood by Sawyer, as they both ate the sweets Meyer and Clembot have given to everyone. Later, as Sawyer and Sceptile were watching the videos, Sawyer cried at his loss, but Sceptile tried to comfort him.
Since roots spouted out and even attacked certain people, Sawyer sent Sceptile, who slashed one of the roots with Leaf Blade. Along with Tierno's Blastoise, Trevor's Charizard and Shauna's Ivysaur, Sceptile helped in escorting the people to safety. Sceptile was with his trainer at a Pokémon Center, where Sawyer watched the broadcast about the Giant Rock. While parting ways, Ash and Greninja recalled their battle against Sawyer and his Sceptile, which they lost.
Sceptile was standing next to Sawyer, who was taking notes from Steven. Ash later remembered his battle in the Kalos League against Sawyer and his Clawitzer, Aegislash, Salamence and Sceptile when he was reflecting back on his journey.
|Razor Leaf -||Battling with Elegance and a Big Smile!*|
|Leech Seed||A Fashionable Battle!|
|Bullet Seed||A Fashionable Battle!|
|Agility||Rivals: Today and Tomorrow!|
|Leaf Blade +||Rivals: Today and Tomorrow!|
|Leaf Storm +||From A to Z!|
|Dragon Pulse||A Meeting of Two Journeys!|
|Frenzy Plant +||Valuable Experience for All!|
|Dragon Claw +||Valuable Experience for All!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.
- ^ a b c XY075: Rivals: Today and Tomorrow!
- ^ XY064: Battling with Elegance and a Big Smile!
- ^ XY073: A Fashionable Battle!
- ^ XY074: Fairy-Type Trickery!
- ^ XY094: From A to Z!
- ^ XY106: A Meeting of Two Journeys!
- ^ XY119: A Full-Strength Battle Surprise!
- ^ XY121: Seeing the Forest for the Trees!
- ^ XY126: Valuable Experience for All!
- ^ XY128: A Riveting Rivalry!
- ^ XY129: Kalos League Passion with a Certain Flare!
- ^ XY132: A Towering Takeover!
- ^ XY135: Rocking Kalos Defenses!
- ^ XY136: Forming a More Perfect Union!
- ^ XY139: Facing the Needs of the Many!
- ^ XY140: Till We Compete Again!