Growing up in the Bavarian Alps, German mutant Kurt Wagner was kidnapped in his early teens by the black ops Weapon X organization. They brutally trained him for months to become their agent. Speaking no English, he was isolated from his fellow captives until the X-Men were likewise kidnapped and the telepathic Marvel Girl communicated with him. When the captives escaped with the assistance of the Brotherhood of Mutants, Weapon X head Colonel Wraith tried to flee in a helicopter. The X-Man Storm blasted it out of the sky in retaliation for his crimes, but Nightcrawler teleported Wraith out, insisting Weapon X had ruined enough lives without turning Storm in to killer as well. The ungrateful Wraith was about to shoot Nightcrawler, but the newly arrived Nick Fury killed Wraith first.
Nightcrawler returned to Germany and learned English, ostensibly from watching television. After mutant terrorist Magneto, long believed slain by the X-Men, resurfaced, the X-Men became fugitives. Their enemies sought out their past associates, including Nightcrawler, who found himself pursued by the German authorities. Evading them thanks to his Weapon X training, he headed for Glasgow and Moira MacTaggert, whose contact information had been given to him by X-Men founder Charles Xavier. He nearly made it to her hideout before being captured and taken to Camp X-Factor in Guantanamo Bay. He was freed by a Brotherhood raid. When Magneto overloaded a Miami nuclear reactor, Nightcrawler was one of many mutants who helped evacuate the area. After the crisis was over, he joined the X-Men. During his time with them, he has hunted the serial killer Sinister, attempted to rescue his kidnapped teammate Rogue from Gambit and the Struckers, bonded with teammate Angel in secret pirate games in the Danger Room as the Dread Pirate Bluetail, and joined an unauthorized expedition to Krakoa to free convicted mutant murderer Longshot.
Nightcrawler and other X-Men Colossus, Dazzler, and Angel went to Kraoka to free Longshot. The X-Men had freed Longshot and escaped not knowing that Mojo had captured Angel. Nightcrawler had teleported them in accidentally dropping Colossus on the way the X-Men fought Mojo and managed to escape with Angel upon learning that Longshot was indeed a murderer it was too late to capture him because he had managed to escape. The team was going to be punished for there action though they new that Dazzler was the reason, Angel stepped up and took the blame knowing that Xavier would not expel him. Much to Nightcrawlers dismay after the incident Dazzler admitted feelings toward Angel.
His close friend Angel admitted his feelings toward fellow X-Man Dazzler as well and the two became a couple, though Nightcrawler himself had feelings for her to. He felt alone because everyone in the mansion had at least some type of romantic connection except him and Colossus. When his then friend Colossus revealed to him that he was a homosexual and dating Northstar, Nightcrawler pretended to be okay with it. But when Dazzler was comatose by Lady Deathstrike, he teleported to her bedside daily and spoke to her saying that he was never okay with it and now avoids Colossus because he is now dead to him.
Recently While visiting Dazzler she had awoken much to Nightcrawlers dismay her first words to him were about the whereabouts of her boyfriend Angel, Kurt teleported from the room back to the mansion never telling anyone not even Angel that Dazzler had awoken.
Afterwards, he kidnapped Dazzler and took her to a cave, seemingly lost his mind. After the X-Men finally find and save Dazzler, she quits the team. Professor X puts Nightcrawler into a deep mental trance to help rehabilitate him. When Rouge breifly touches Nightcrawler, she calls him a monster and runs away screaming.