Prior to the start of the series, Blue received Charizard as a Charmander from has grandfather, Professor Oak. Although he was given as a Starter Pokémon, Charmander was not Blue's first Pokémon, as he already owned Scyther. Charmander was with Blue when he went to Chuck for intensive training.
Charizard first appeared as a Charmander in A Glimpse of the Glow. Blue tried using him against a Mew but failed and withdrew him partly due to Red accidentally catching his attention, which resulted in Poli's embarrassing defeat.
At some point before Onix Is On!, Charmander evolved into Charmeleon, and battled Brock in the Pewter Gym, which he apparently won, as Red states that he and Blue were the only ones to win the Boulder Badge.
In That Awful Arbok!, Blue and Charmeleon became possessed in the Pokémon Tower by a Gastly. Red shows up and manages to save the two, at which point they head further into the tower. They eventually run into Koga and his Arbok. Blue has Charmeleon attack Koga, but it proves to only be a projection, with Koga being elsewhere. Koga sends Arbok after them and attack with Acid. Charmeleon counters with Reflect, and outside the tower Koga observes the battle from a Golbat-shaped screen and commands another Acid that appears to break past Charmeleon's defense and corrode him. Koga gloats at his victory, but is soon surprised as Charmeleon slices Arbok cleanly in two.
In A Tale of Ninetales, Charmeleon is accidentally traded to Red alongside Blue's other Pokémon. During the three days that Red has them he attempts to get them to relax and open up to him, with little success. They later traded back, while keeping the caring attitude that Red installed in them.
In Kalling Kadabra, it is revealed that Charmeleon has evolved into Charizard. He was seen being used by Blue to try and fly into Saffron City. He later helped defeat Koga by melting his ice-cold Blizzard room by setting the whole building on fire. After this Charizard is used alongside Saur and Blasty to help defeat Thu-Fi-Zer.
In A Charizard...and a Champion, Charizard was Blue's first choice in his battle against Red and his Saur during the Pokémon League. Blue orders a Fire Spin that Saur barely dodges, but as Charizard lunges in for a follow-up attack Saur surprises it with a burst of Poison Powder. Red follows with a Razor Leaf that Blue is forced to assist his addled Charizard in dodging, before switching for Machamp to continue. He is later sent back out to fight against Saur once again, but was defeated due to a combo attack from Poli, Saur, and Pika, who had created a thundercloud that struck Charizard from Saur's Vine Whip.
In As Gastly as Before, Charizard defeated a Gastly that was attacking Yellow. He is later seen training with Blue and Scyther.
In Striking Golduck, Charizard is used alongside the rest of Blue's team to attack Agatha's Gengar. Despite a group attack Gengar escapes into Blue's shadow and attacks Charizard. Not wanting to give Gengar more places to hide Blue calls all his Pokémon back.
In The Legend, Charizard is used alongside Saur and Blasty to help Yellow defeat Lance's team.
In Rock, Paper...Scizor, Charizard is traded to Red for his Gyara so that he could make it across the ragged mountains of Mt. Silver.
In The Last Battle XIV, Charizard is returned to Blue and was used in the final battle against the Masked Man.
In Return to Pallet Town, Charizard battled alongside Saur against Organism No. 1. Due to Organism No. 1's impressive speed, neither of them were able to land an attack before the DNA Pokémon fled.
In the Sevii Islands during My, My, My Mimic, Charizard learned the move exclusive to the Fire-type starter families, Blast Burn, after training on Ultima's Jump Path, Catch Path, and Battle Path courses. Afterwards, the two boys' inability to perfect their respective move's accuracy would come to haunt them in the battle against Sird, Carr, and Orm.
In Put Your Beast Foot Forward, Blue sent Charizard out to use Flamethrower on Orm's Shuckle, but fails due to their hard shells. Several Shuckle soon pop out of the ground and attack him with Toxic.
Charizard still managed to gather the strength to fight and participated in the battle on Trainer Tower in Meet Deoxys, and Deoxys, and Deoxys, and... against Organism No. 2's clones. Charizard then agreed to be traded to Red again to allow Red to Fly and defeat the evil leader as Red's Aero was too badly injured from its earlier encounter with Organism No. 2 and therefore couldn't use Fly in his current condition.
In Distant Relation Deoxys and Storming the Forretress, Charizard was seen joining Red's other Pokémon and Chuchu to take down the ten Forretress that Carr had placed inside the Team Rocket airship. After Giovanni's defeat, Charizard was traded back to his original owner, but the two soon found themselves petrified by Sird with the four other Pokédex Holders and their Pokémon.
In The Final Battle VIII, Charizard becomes unpetrified and regained mobility, upon which Charizard, Exbo, and Chic attack with Blast Burn to help destroy Guile Hideout's fake Kyogre.
Charizard appears with Blue in Pinsir Glares, helping Blue rescue Diantha. He, along with Rhyperior, later leads X's group to Anistar City. While doing so they are admired by Salamè and Rhyrhy and after exiting Route 17 they leave them and return to Blue.
In Charizard Transforms, on the route to the Pokémon Village, the group was attacked by Xerosic. During the battle Blue assists X in the fight and reveals to everyone that he also possesses a Key Stone given to him from Gurkinn. Together with X's Salamè, Blue and X use their Key Stones to Mega Evolve both of their Pokémon into Mega Charizard Y for Blue and Mega Charizard X for X. The combined might of both Mega-Evolved Pokémon easily defeats Xerosic. Charizard later tries to help suppress Mewtwo's rage at the Pokémon Village alongside Rhyperior, Marisso, and Salamè. Despite their numbers Mewtwo keeps the advantage, easily knocking them away with Psywave.