Harrison received Blaziken as a Torchic when he started his journey in Hoenn. Blaziken's first on screen appearance was when it battled and defeated a Sneasel allowing Harrison to capture it. At the time, Ash's Pokédex was unable to identify Blaziken since it was from the Hoenn Region.
Blaziken later appeared to battle Ash's Bayleef and Charizard. It casually grabbed Bayleef's Vine Whip and effortlessly pulled her towards it before knocking her out with Fire Punch. Charizard provided a far greater challenge, beginning the battle with Flamethrower and Blaziken countered with the same move. Then Blaziken displayed its incredibly jumping abilities by dodging Charizard's next Flamethrower and using Quick Attack in midair. Charizard flew up to avoid it and Blaziken fired another Flamethrower which Charizard narrowly avoided. Once again the two Fire types fired Flamethrowers at each other and were evenly matched. Blaziken and Charizard then started trading blows, dodging and striking each other repeatedly until Blaziken tried to hit Charizard with another Quick Attack. Charizard dodged it but Blaziken skidded to a halt, turned, and smashed a Fire Punch into Charizard's face. Charizard struck back with another Flamethrower before dodging the next Quick Attack and hitting Blaziken with his tail. Charizard then grabbed Blaziken and hurled it to the ground with Seismic Toss. For a moment it seemed that Charizard had won but then Blaziken stood up, battered and bruised but far from defeated. It landed another Quick Attack, endured Flamethrower, and leapt into the air when Charizard tried another Seismic Toss. Charizard flew after Blaziken but was caught off guard by a Blaze Kick attack. Blaziken fired another Flamethrower, intending to finish the battle and Charizard countered with Dragon Rage creating a massive explosion. When the smoke cleared both trainers encouraged their Pokémon to stand up. With a considerable amount of effort, Blaziken managed to get back to its feet and Charizard did the same a few seconds later. However when Charizard tried to use another Flamethrower, he was overwhelmed by all the damage he had taken and fainted.
Although Blaziken had defeated Charizard, it had been badly hurt in the process and Harrison refused to allow it to fight in the next round out of concern for its condition. Since he didn't want to risk having Blaziken get hurt even more badly than it already was, he lost the next round.