Herdier is a light brown, canine Pokémon with a short snout. Its face has long, cream fur, which forms a mustache and a three-pointed crest. Its ears are large and perked, and it has a black nose. It has shaggy dark blue fur covering its body and a short tail. This hard, thick fur serves to protect Herdier from attacks. It has four short legs, with three-toed paws. Each paw has a dark blue paw pad that can be seen in Pokédex 3D Pro.
Herdier is very loyal, smart, friendly, and it will help its Trainer raise other Pokémon. However it will not obey anyone who disrespects it, It has helped Trainers since long ago. Herdier has been theorized to have been the first Pokémon to have been partnered with humans based on what was discovered on the walls of caves. Its dense fur continues to grow endlessly. As Herider's fur grows, it becomes more springily and impervious. Any claws or fang attempting to penetrate its fur would just bounce off. However, the fur makes Herider difficult to train due to how much it costs to groom its dense fur.
Herdier debuted in Rematch at the Nacrene Gym!, under the ownership of Lenora. It battled against Ash and his Tepig during a Gym battle, but it was eventually defeated by Tepig's Flame Charge.It reappeared in a flashback in Certain Up, Unova League!.
In A Venipede Stampede!, the Officer Jenny of Castelia City used two Herdier during an effort to curb the tide of invading Venipede.
In There's a New Gym Leader in Town!, Cheren's Herdier defeated Ash's Oshawott with Thunder Fang during an unofficial battle.
In Deceiving Appearances!, Lusamine kept a Herdier as company in her office at the Aether Paradise mansion. It reappeared in a flashback in Mission: Total Recall!.
In Ash and Trip's Third Battle!, Trip's flashback featured a Herdier being defeated by Alder's Bouffalant.
A Herdier appeared in a flashback in White—Victini and Zekrom and Black—Victini and Reshiram.
A Herdier appeared in Ash Versus the Champion!, under the ownership of an Officer Jenny.
A Trainer's Herdier appeared in Cilan Takes Flight.
A Trainer's Herdier appeared in Climbing the Tower of Success!.
In Kyurem VS. The Sword of Justice, Kanata's Herdier lost a battle against Misaki's Liepard in the Roshan City Pokémon Center. Another Herdier appeared during the Swords of Justice legend.
A Trainer's Herdier appeared in Curtain Up, Unova League!.
Two Herdier appeared in Team Plasma's Pokémon Power Plot!, with one under the ownership of a Trainer and the other appearing in a flashback.
In Genesect and the Legend Awakened, a Herdier was living in Pokémon Hills.
A Trainer's Herdier appeared in Thawing an Icy Panic!.
Two Trainers' Herdier appeared in Alola to New Adventure!.
A Trainer's Herdier appeared in A Shocking Grocery Run!.
In Young Kiawe Had a Farm!, a Herdier herds all of the Pokémon at Paniola Ranch, which is owned by Kiawe's family. In The Young Flame Strikes Back!, it barked at Viren and his Electivire as they arrived.
In Racing to a Big Event!, a Trainer's Herdier competed in the Pokémon Pancake Race.
Two Trainers' Herdier appeared in Crystal-Clear Sleuthing!.
Two Trainers' Herdier appeared in One Journey Ends, Another Begins...
A Trainer's Herdier appeared in Getting the Band Back Together!.
A Trainer's Herdier appeared in A Glaring Rivalry!.
A Herdier appeared in Treasure Hunt, Akala Style!.
A Trainer's Herdier appeared in Faba's Revenge!.
A Trainer's Herdier appeared in Real Life...Inquire Within!.
A Trainer's Herdier appeared in Sours for the Sweet!.
In Don't Ignore the Small Stufful!, a Herdier was at Aether Paradise.
A Trainer's Herdier appeared in We Know Where You're Going, Eevee!.
In Battle Royal 151!, a Trainer's Herdier competed in the Battle Royal preliminary round of the Manalo Conference, but it was defeated by Sandy and Shaymin.
In Battling on the Wing!, a Trainer's Herdier watched the battles of the Manalo Conference. Another waited in line with its Trainer for Team Rocket's food truck.
A Trainer's Herdier appeared in Exhibition Unmasked!.
A Trainer's Herdier appeared in Raid Battle in The Ruins!.
In A Little Rocket R & R!, two Trainers' Herdier were captured by the Matori Matrix but later freed by Ash and his friends.
A Trainer's Herdier appeared in A Close Call... Practically!.
||Herdier, the Loyal Dog Pokémon, and the evolved form of Lillipup. Herdier's hard black fur softens its opponent's attacks like armor.
||Herdier, the Loyal Dog Pokémon and the evolved form of Lillipup. Always obedient and faithful to their Trainers, Herdier have helped them raise other Pokémon since long ago.
A Herdier appeared in The Uprising, under the ownership of Lenora.
Two Herdier briefly appeared in The Plan, under the ownership of a Trainer who was listening to Ghetsis's speech in Accumula Town.