Saur first appeared as a Bulbasaur in Bulbasaur, Come Home! inside Professor Oak's Lab. Red enters Professor Oak's Laboratory in hopes that the professor would teach him how to be a great Pokémon Trainer, and finds a dark, empty laboratory. In one of the Poké Balls he finds on an empty table is Saur. Professor Oak soon enters and startles Red, causing him to accidentally release all of Professor Oak's Pokémon from his lab. After Red caught back almost all of Oak's Pokémon, Red found Saur in the closed Viridian Gym. Saur was scared, but Red used calming words to gain his trust, which caught Oak's interest, as in the past the Bulbasaur was disobedient to the level of using Tackle on him. Disaster struck as a wild Machoke appeared and attacked them, When all bets were off, Red took a wild guess and presumed that with the giant seed on Saur's back being its key trait, exposing him to rays of sunlight would be worth an attempt, and opened the curtains on the window, allowing him to use Solar Beam and defeat the bulky Pokémon in a flash. After the battle, Professor Oak saw the bonding occurring between Saur and Red, as well as the fact that Saur had learned how to use Solar Beam, and allowed Red to keep him, along with a Pokédex.
In Onix is On!, Saur was used alongside Poli and Pika to help Red in his Gym battle to win the Boulder Badge. Saur was shown being used to defeat an opponent's Sandshrew. Saur was later used in Suddenly Starmie to fight against Misty's Starmie in order to win the Cascade Badge. Saur attacks with a Vine Whip attack but Starmie shrugs it off and defeats him with Bubble Beam.
He evolved into Ivysaur in Wartortle Wars at the gates of Celadon City, when he battled an attacking Primeape. Green, distracting Red with fake applause for this evolution, sold Red a bunch of fake items that did nothing but hinder him. Red proceeded to give chase on Green to get his money back, while Green used the opportunity to steal Red's two Badges. However, a chain of events unfolded in the Rocket Hideout, that left Red (disguised as a Team Rocket Grunt) and Green allied. Saur's Vine Whip was used to try to capture the Mew that appeared before them. After they managed to save Mew from being caught by the Rockets.
In A Tale of Ninetales, Saur is accidentally traded to Blue alongside Poli and Pika. During the three days that Blue has them he trains them vigorously. They later traded back, while keeping the serious attitude that Blue installed in them.
In Meanwhile…Vileplume!, Saur is used in Red’s Gym battle against Erika in his fight to save Eevee. Red commands Saur to use Vine Whip and reel Tangela in, but Tangela tosses Saur away with little effort and defeats him.
In Kalling Kadabra, Red returns to Professor Oak's lab in order to find a way into Saffron City. The professor starts attacking and in response Red releases Saur to restrain Professor Oak with Vine Whip, but Professor Oak surprises them by exhibiting signs of Psychic power, and attacking Saur with a Psybeam. Recognizing the handiwork of a Psychic-type Pokémon, Red orders a Leech Seed from Saur, and as the "Professor's" energy is drained away it reveals itself as a Kadabra, which had been using its illusionary Hypnosis powers on Sabrina's command. As the Gym Leader herself appears, she graces Red with a warning before teleporting away. Before she teleports, Saur uses Razor Leaf, but it goes right through Sabrina without doing anything to her. Saur was later used to battle against Lt. Surge and Zapdos in Zap! Zap! Zapdos!. Saur's attempts to fight back with Razor Leaf seem hopeless until Red has Saur redirect the leaves it scattered from its Razor Leaf at Lt. Surge and Zapdos. The attack not only severs the wires directing Zapdos's electric power away from Surge, but also ruptures the Gym Leader's insulated suit, giving him a crippling dose of Zapdos's electricity that promptly knocks him out cold.
In The Winged Legends, Saur, Blue's Charizard, and Blasty battle against the the merged version of Zapdos, Moltres, and Articuno. During the attack Saur evolves into Venusaur, which tips the scales of the battle towards the three starters's favor, and eventually defeats Sabrina, and also separates the conjoined legendary Pokémon.
In A Charizard...and a Champion, Saur is Red's first Pokémon used in Red's battle against Blue and his Charizard in 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 Snor to continue. Saur is later sent back out against Charizard. Following Poli and Pika, he was able to defeat Charizard by using the thundercloud created by his teammates in conjunction with his Vine Whip acting as a lightning rod.
Saur was seen in Red's battle against Bruno in Can You Diglett?, battling against his Onix. Saur used its vines to cover the ground, ready to defend against Onix. The moment Onix came up, Saur used all its vines to push Onix back. Suddenly, Onix's tail comes up from behind Red and smashes into him and Saur, sending them underground. Underground, there are several holes that Onix could come through. When Onix appears, it starts to charge at Saur. Saur braces itself, but is not hit as Bruno stops the battle.
Saur was seen in Forretress of Solitude, being used in Red's test to become Viridian City's Gym Leader. Saur first goes up against a Pineco, which he swiftly knocks out, as well as his next two opponents, a Forretress and another Pineco. However, the fourth opponent, another Forretress, resorts to its Spikes and puts up a fair fight against Saur. Red commands Saur to use Sweet Scent, then promptly switches it out for Snor.
In The Last Battle XIV, Saur is used in the final battle against the Masked Man. After the fight was over, he was taken to Mt. Silver to train with Gold.
In the Sevii Islands, Saur learned the move exclusive to the Grass-type starter families, Frenzy Plant, 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. When Deoxys appeared, Saur nearly died shielding Red from the fearsome Pokémon's Psycho Boost attack.
Saur 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 Deoxys' clones. Saur then agreed to be traded to Blue again to allow Red to Fly on Charizard and defeat the evil leader. After Giovanni's defeat, Saur 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, Saur becomes unpetrified and regained mobility, upon which Saur, Megaree, and Emerald's Sceptile attack with Frenzy Plant to help destroy Guile Hideout's fake Kyogre.
In PAORAS11, Saur is revealed to have gained the ability to Mega Evolve into Mega Venusaur. He is used alongside a Mega Evolved Blasty to battle Archie and Maxie.