|First Appearance:||Mega Man X|
 Classic Series
After the events of Mega Man 2: The Power Fighters, Bass Heads back to Dr. Wily's lab. The doctor explains to Bass that he is no longer needed, because he has made the ultimate robot out of Bassnium, the material used to create Bass. A silhouette of Zero is shown. Bass laughs at Zero's long "girlish" ponytail, and writes him off as another one of the Doctor's failed experiments.
 X Series
Zero is the leader of the Maverick Hunters. During Sigma's raid on the city, he helped Mega Man X, who was recently released from his capsule and still not strong enough to fight by himself. Zero then gave him some words of encouragement and left to find more information on Sigma and his secret fortress. After finding the fortress, Zero was amazed at how much strength X had gained. Unfortunately, when X and Zero encountered Vile, Zero was badly damaged. X defeated Vile after a hard struggle only to watch Zero fade away into the shadows. Six months later, a group of mavericks known as the "X-Hunters" formulated a plan to revive Zero and turn him into a maverick. That plan was called " The Unification". In a nutshell, the plan was to bring back Zero to life and replace Sigma. However, thanks to X, their plan failed and Sigma was revived instead. Zero recovered fast enough to help X defeat Sigma.
A year later, with the knowing of robot scientist, Dr. Doppler, the city and Maverick Hunter headquarters were attacked. X and Zero rushed to Doppler's island. X and Zero fought hard against Doppler's army and even found his secret lab. What X and Zero found out that it was Sigma taking on a form of a computer virus is what caused this crisis. Both X and Zero defeated Sigma again, Zero hopes that it would be the last of Sigma.
Then, a new reploid army was formed thanks to Dr. Cain, it was called Repliforce. Maverick Hunter had formed an alliance with this new army, Zero is in particular, as he made a friend in the army's best soldier, Colonel, and developed a small romantic relationship in Colonel's sister Iris. However, Zero began to have painful nightmares about the scientist who created him, both Maverick Hunter and Iris are trying to discover this. Then, when the time came that the Sky Lagoon was attacked, Repliforce was responsible for this latest attack, X and Zero rushed to the scene, only to find out that it was falling to the ground, in the ruins of the Sky lagoon, X Fought the dragon, while Zero searches for Iris. Then, Zero was given orders to scramble and stop Repliforce, Iris volunteered to be Zero's adviser, then Colonel sent him a message, to meet him at monument hall, but before the two fought, Iris broke it up, but Zero knows that he must be stopped. He eventually fought Colonel again, but this time, Zero was victorious, he also fought Iris after she found out about her brother, it was not long that he found Sigma and fought him as well, then he escaped the final weapon just before X did, and wonders if all reploids are destined to suffer the same fate.
Zero still has the same nightmares and thinks about Iris. But, his visions on Iris had caused Zero to conclude on who was in his nightmares, he was created by Dr. Wily. Then, when the Eurasia incident began, he rushed to the colony, then, he finds that it was a collision course with Earth, but the only solution is to fly a shuttle to the colony, Zero volunteers and directed the shuttle to the colony, the colony was destroyed, but is now severely damaged, then Zero and X fight Sigma again. Then, with his last ounce of strength, Zero defeats Sigma, but remained in shadow, X believes that Zero is dead. 3 weeks later, a phenomenon called the "Zero Nightmare" occurs, many believe that it was Zero's ghost. But, X investigated, and fought the nightmare, only to find out that it was really Zero. Overjoyed, X greets Zero back and the two fought the scientist Gate and Sigma.
A few months after, Zero became the leader of the Maverick hunters again after X stepped down from that duty, then Zero did some investigation over the highway were he found X, and found another reploid named Axl, with that the 3 (X, Zero and Axl) fought a new breed of mavericks and eventually Sigma.
 Zero Series
The Zero Series takes place in an alternate universe about 100 years after the "X" series. Zero is sealed away in a capsule until it was opened by a human women named Ciel. Ciel was a leader of a resistance army which faced against Neo-Arcadia. In the end of Mega Man Zero 4 it appears that Zero has died.
 ZX Series
Zero makes an appearance in the ZX series as Model Z, who plays a minor supporting role in the plot in the first ZX game. In Mega Man ZX, Zero appears in a flashback in Vent's story. Prairie explains that her sister was a human (referring to Ciel) the protected reploids. Zero is mentioned again when Piaraie explains that Model W is the spirit of Dr. Weil.
In ZX Advent, Zero plays a smaller role. He only has a few lines throughout the game.
 Battle Network Series
Zero also appears in MegaMan Battle Network, but this time as Zero.EXE. Also this time he's the virus. In the beginning of the game he is a bad guy, but later on he helps Mega Man.
 Other Appearances
- Mega Man Zero's version of Zero's character appears as a sub-boss in Playmore's crossover fighting game SNK vs. Capcom: SVC Chaos.
- He also appears as a hidden character in Onimusha Blade Warriors.
- A poster of Zero appears in Higsby's shop in MegaMan Battle Network 3 White version.
- A poster of Zero, in his "Black Armor", can be seen in the store of Yosyonke City in the game Mega Man Legends 2
- The X version of Zero appears in Tatsunoko vs. Capcom: Ultimate All-Stars.
- The X version of Zero also appears in Marvel vs Capcom 3: Fate of Two Worlds.