Appearing in Snivy Plays Hard to Catch!, Snivy was discovered by Ash and his friends after she stole some cake from them. Iris and Cilan speculated that Snivy abandoned her Trainer who she deemed unworthy, as she was clearly demonstrating a high level of competency and skill, evident in her first escape from Ash by infatuating Pikachu with Attract then escaping using Leaf Storm. She also snickered at Ash in his first attempt to capture her.
Ash was able to capture Snivy when he won her respect, and was recognized before her eyes as a Trainer of not only skill, but of qualities like his unwavering determination and overpowering spirit. Despite his countless defeats with Snivy, especially when the majority of his team (Pikachu, Oshawott, Tepig) succumbed easily to her Attract, Ash nevertheless followed her all the way throughout from the time they met to the point of her capture. During this journey, Ash showed her two notable acts of sacrifice: the first when he shielded Pikachu from her Vine Whip, and the second when he asked Pikachu to climb onto his head when they were sinking into a muddy swamp. At last, Ash had to perform a show of skill before he could capture her. Luckily for Ash, Pidove was also female and was not affected by Attract, allowing him to battle on even grounds. In the battle that ensued, Snivy put up a strong struggle against her captor but was weakened considerably. Despite seemingly being in visibly good condition, she finally let out a small, humble smile that signified the acceptance of her Trainer, before allowing Ash to capture her.
Snivy was sent out twice during Ash's 5-on-5 battle with Trip in A Rival Battle for Club Champ!. In her first match against Trip's Servine, her use of Attract predominantly paved her way to victory after her opponent successfully became infatuated with her. Later on she was called upon to battle Trip's Frillish, and Ash, who had no knowledge of his opponent's Ability, Cursed Body, commanded Snivy to use physical attacks which ultimately led to their loss.
In Emolga and the New Volt Switch!, Snivy was called out of her Poké Ball by Iris's Emolga's Volt Switch. Since Emolga did not wish to battle anymore, Ash used Snivy in a battle against Bianca's Pignite for a short period. Later during lunch, Snivy noticed that Emolga tricked her male teammates into giving their lunch to her and ratted her out to Ash and company. Later, she noticed that Emolga had wandered away, as well as Axew and Oshawott after her, and decided to investigate. Snivy found them being attacked by an angry Simisear and stopped it with Vine Whip. Emolga did not wish to fight Simisear, but Snivy forced her to help out. When Snivy was hurt by Simisear, Emolga finally decided to assist her and the two Pokémon worked together to stop it. They also saved Simisear's life by doing a Hidden Power-Leaf Storm combo to destroy a boulder that was about to crush it. Both Snivy and Emolga later temporarily settled their differences and shared an apple to symbolize that.
She battled with Trip's Servine once again in Ash and Trip's Third Battle!. This time around Trip and Servine were prepared for Attract and countered it with Leaf Tornado. She was then taken out of the match with a single Cut from Servine.
In Cilan Versus Trip, Ash Versus Georgia!, Snivy was used against Georgia's Pawniard during the second round of the Club Battle Tournament, however, she struggled against the powerful Pokémon, having Attract fail when Pawniard also turned out to be female. However, she managed to defeat Pawniard in the following episode with Leaf Storm.
In Battle For The Underground!, when Pikachu spotted her Poké Ball among those Team Rocket had stolen from the Nimbasa Pokémon Center, he used Electro Ball to let her out. Snivy searched through the pile of Poké Balls, looking for the others, letting out Excadrill to free Pikachu and Axew from their cages, Pansage to help bust through the door, Dwebble at Pikachu's request to burn from the sturdy door, and Tepig and Roggenrola to propel the train cart away from Team Rocket. She later helped fight off Dr. Zager's helicopter while the other Pokémon tried to work out an escape.
In Dazzling the Nimbasa Gym!, Ash used Snivy in his Gym match against Elesa and her Emolga. They were both female, so Attract proved to be ineffective. Despite trying her best, none of Snivy's attacks were working and in the end, Emolga defeated Snivy with a barrage of powerful Aerial Ace and Acrobatics attacks.
In Scraggy and the Demanding Gothita!, Snivy looked happy to see Ash's Scraggy and Iris' Axew getting along happily. In the middle of the night when Katharine's Gothita escaped with Scraggy, and then followed by Axew, Snivy closely followed them all and helped protect them from a wild and angry Garbodor that Gothita had disturbed. Snivy scolded Gothita and battled Garbodor until Katharine's Deerling calmed it down with Aromatherapy. The next day, Snivy had a battle with Gothita, which resulted in a clear victory for Snivy. Snivy then condemned Gothita's loss, making it run away in a fuss with its Trainer close behind.
In Stopping the Rage of Legends! Part 1, Snivy battled Tornadus and Thundurus in an attempt to halt their rampage. She landed a hit on the legendary Pokémon by combining her Leaf Storm with Excadrill's Drill Run, but was eventually defeated by the powerful opponents.
In Battling the King of the Mines!, Snivy was Ash's second Pokémon in his Driftveil Gym battle against Clay, she went up against his Palpitoad, since she was strong against both Water-type and Ground-type, she used her Attract to infatuate Clay's Palpitoad, which worked as he was male, she used her Vine Whip and Leaf Blade attacks to hit Palpitoad, he was then revealed to still be infatuated allowing Snivy to finish off the Vibration Pokémon off with Leaf Storm, this annoyed Clay who thought Ash's strategy wasn't right as it wasn't an upfront assault. In response he used his most powerful Pokémon, his Excadrill, Snivy used Vine Whip but this was blocked by Excadrill's Rapid Spin. Her Leaf Blade, Attract and even her Leaf Storm were countered in the same way, causing Excadrill's Rapid Spin to hit Snivy. The Subterrene Pokémon then used its one-hit knockout move, Horn Drill, which defeated Snivy.
In Evolution by Fire!, Snivy was disgusted at Shamus, Tepig's former Trainer, for his treatment of her friend and volunteered to battle as Tepig's partner with Shamus's Emboar and Heatmor the next day. That night, she confronted Tepig and slapped him with Vine Whip in an attempt to snap him out of his depression and encouraging him. When she was sent out to battle Shamus's Pokémon, Snivy was more than ready to fight and defend Tepig's honor, while Tepig didn't feel as motivated. While shouting words of encouragement to Tepig, who wouldn't dodge his opponents attacks, Snivy was hit by her opponents' powerful attacks, wearing her down severely. When Shamus ordered a Flare Blitz/Fire Spin combination attack, Snivy pushed her friend out the way of the attack, taking a lot of damage and being knocked out. Though she was unable to battle, Snivy insisted that she stay outside of her Poké Ball, and watch the end of the battle. This motivated Tepig to evolve into Pignite, learn Fire Pledge, and defeat his opponents.
In Cameron's Secret Weapon!, Snivy was the sixth Pokémon Ash chose to use during his Vertress Conference battle with Cameron, sending her out to face Cameron's Riolu. Riolu started the battle with a Vacuum Wave, which Snivy was easily able to dodge before attacking the Emanation Pokémon with Leaf Blade. Riolu, however, quickly recovered and used Copycat, striking Snivy back with her own attack. Next Riolu used Vacuum Wave again, forcing Snivy to jump out of the way and allowing Riolu to easily grab her in order to use Force Palm on her. Before Snivy could recover from the hit, Riolu carried on with a Circle Throw, sending the Grass Snake Pokémon flying into the arena wall. Snivy, however, just got mad for getting thrown around, and started a comeback. First she fired a Leaf Storm, forcing Riolu to dodge it and allowing her to grab the Emanation Pokémon with Vine Whip and slam it into the field. Riolu then fired another Vacuum Wave attack, which made a direct hit. But when it tried to repeat the same move, Snivy used Leaf Storm to counter it. The Grass-type attack overpowered the Fighting-type move and hit Riolu, causing serious damage. Unfortunately for Snivy and Ash, this resulted that Riolu suddenly evolved into Lucario, a much more formidable opponent. When the battle continued in the next episode, Snivy fought bravely against her evolved opponent, hitting it with Leaf Blade and Vine Whip. Despite of this, Lucario hit back with Force Palm, swung Snivy around by her own Vine Whip, and finally finished her off with its newly learned Aura Sphere.
In Team Plasma and the Awakening Ceremony!, Snivy was sent out alongside the rest of Ash's team to help Ash and N dig up to the surface of the White Ruins after they had fallen into a pit. While battling Team Plasma, Snivy dealt massive damage to two controlled Golurk with her Leaf Storm attack. However, when Colress turned his mind control machine on them, Snivy was quickly recalled to her Poké Ball along with Ash's other Pokémon.
In Team Rocket's Shocking Recruit!, Snivy joined the gang to search for Emolga, who had run off after being unfairly shouted at by Iris for attacking Axew. When they later found Emolga with Team Rocket, Snivy and Emolga began to argue and battle each other. Snivy deflected one of Emolga's Hidden Power attacks which flew off course and disturbed a sleeping Exploud. The Loud Noise Pokémon emerged from the bushes and began to attack the gang, allowing Team Rocket and Emolga to escape with Axew. The gang later found out that Emolga had not been in the wrong and had actually been protecting Axew, leaving Snivy a little embarrassed over assuming the worst of her rival. Snivy helped to save the day by hitting Woobat and Yamask with a frenzy of Vine Whip attacks and a powerful Leaf Storm before freeing Pikachu with Leaf Blade. After Team Rocket had blasted off, Snivy reluctantly and sharply apologized to Emolga.
Snivy was reunited with the entire Unova team at Professor Oak's Laboratory in The Dream Continues!. She joined the others in a group attack on Team Rocket with her Leaf Storm to send them blasting off for the last time in the Best Wishes series. Snivy was left at the lab before Ash set off for the Kalos region.