Ash caught Corphish in the episode Gone Corphishin'!. Ash and his friends were camping on a beach, and Corphish was attacking them from underneath the sand. Eventually, its identity was revealed and Ash battled it and caught it using his Treecko.
In the next episode, when Corphish met the gang's other Pokémon, it struggled to make friends, smacking the others to greet them and eating their food. In the same episode, Corphish fell ill and was carried to the Dewford Town Pokémon Center by its new trainer Ash. The next morning, it had recovered and was able to stop Team Rocket's plan. Corphish had its first Gym battle in Just One of the Geysers against Brawly, where it was chosen to battle his Machop, Corphish won the battle but still fell to Hariyama.
It battled Flannery in Going, Going, Yawn, where it was Ash's first Pokémon used in the battle and faced Flannery's Magcargo and won but was then put to sleep by her Slugma's Yawn attack, but later it woke up to beat her final Pokémon, Torkoal.
In It's Still Rocket Roll to Me, Corphish saved Max and one of the Mossdeep Gym Leaders, Tate, when they were captured on board in a space shuttle by Team Rocket.
In Once in a Mawile, it fell in love with a Mawile, however the feeling was not mutual as the Mawile was in love with Brock's Lombre. It teamed up with the also heartbroken Brock to sing and dance to "Brock's Paradise" in order to keep an audience entertained.
In The Great Eight Fate!, it replaced Snorunt, in Ash's double battle against the Gym Leader, Juan. Teamed up with Pikachu, they were able to defeat the powerful combo of Sealeo and Seaking, allowing Ash to go on to the second stage of the Sootopolis gym battle. In the next episode it defeated Juan's Luvdisc, only to be flattened by his Whiscash's Rock Smash.
In the Ever Grande Conference, it was used in several battles. It first teamed up with Torkoal in From Brags to Riches to battle Dominick, after Torkoal fainted, Corphish was on its own to defeat Swalot, which it did by using BubbleBeam in Swalot's mouth. It later battled Katie and her Golduck in A Judgment Brawl and manages to defeat it while it was confused, but when Katie sent out her Venomoth again, Ash recalled Corphish as it was still confused. It later came out to battle Walrein but was beaten quickly. Ash chose Corphish to battle his rival Morrison, where it easily defeated his Girafarig when Morrison refused to order an attack, then in the next episode, it beat his Growlithe in the same way before Ash was able to snap Morrison out of his hesitation. Afterwards, Corphish then tied with Morrison's Swampert. In Ash's battle with Tyson in At the End of the Fray, Corphish battled his Hariyama but quickly lost.
Back at Pallet town in The Right Place and the Right Mime, it met and soon made friends with Ash's other crab-like Pokémon, Kingler.
In Tactics Theatrics!!, it teamed up with Swellow to battle Dome Ace Tucker and won Ash the Tactics Symbol.
In Talking a Good Game!, it battled Anabel's Alakazam and lost. In the next episode however, it was able to beat Alakazam in a rematch, only to be beaten by her Metagross.
Corphish danced with Brock to the same song as they did in Once in a Mawile, albeit a new version, in Strategy Tomorrow, Comedy Tonight.
Ash left Corphish at Professor Oak's lab when he left for Sinnoh.
It reappeared in An Old Family Blend!, alongside Ash's other Pokémon. It helped to battle against one of Team Rocket's mechas by using its BubbleBeam. It also helped to put out a fire, along with Totodile and Piplup, that was accidentally started by Cyndaquil. Corphish was not seen participating in the Lily of the Valley Conference.