Vincent was once a member of the Turks thirty years before the events of Final Fantasy VII. He was assigned to supervise The Jenova Project in Nibelheim, where he fell in love with a scientist named Lucrecia Crescent, an assistant to Professor Hojo.
At first unknown to Vincent, Lucrecia once was an assistant to his father Grimoire Valentine on the discovery of Chaos and Omega, but Grimoire died saving her life when the tests of the experiment went wrong. Vincent later discovered her link with his father's death and asked Lucrecia why she never told him. She fled from Vincent, but he wanted to find her so he could tell her his true feelings for her. When he spoke to Lucrecia later, she didn't want to be with him as she felt too guilty about his father's death. She told him it was all her fault, and fled again, ultimately entering a relationship with her associate Hojo instead. Lucrecia became pregnant afterwards, and her unborn child was to be part of the next Jenova experiment of Hojo's, which was an investigation into the effect of Jenova cells on an unborn child. Vincent was strongly opposed to this and confronted Hojo to ask him if what he heard was true. As Lucrecia entered, Hojo lied to Vincent saying it had nothing to do with him and that they were scientists. Vincent asked Lucrecia if she was sure it was what she wanted, and she retorted that if it concerned only her then yes, she was sure. So, in the interest of science, she decided to proceed with the treatment. After a while, Lucrecia became very sick and started to see visions of what would become of her unborn son in the future. Outraged, Vincent confronted Hojo in the Shinra Mansion's underground laboratory. Hojo, being angered with Vincent's approach, pulled out a gun from his lab coat and shot Vincent in the stomach. He proceeded to use his body as the subject for experiments that involved making his body stronger and capable of metamorphosis. Hojo's experiment, however, ended up being only a partial success. Although he was able to make Vincent both stronger and able to alter his anatomy, he was still dead all the same in the end. But Lucrecia, who had felt guilty for being unable to help him, went into the lab where Vincent was located to try to find a way to save him. Lucrecia started to look through her unfinished thesis on Chaos, Omega and the Lifestream. Hojo caught her looking at her files and said to her that she just wanted to use him so she could finish her thesis because of how people thought it was so "unrealistic". Lucrecia didn't want to believe she was doing it for that, so she persisted so she could try to save him. Lucrecia injected him with stagnant Lifestream which revived Vincent and turned him into the beast Chaos. He was able to be such a perfect host for Chaos because Hojo made his body so strong (immortal). However, due to Chaos becoming violent and nearly attacking her, Lucrecia put the materia called "Protomateria" inside him to keep Chaos and its feral nature under control. Lucrecia left and tried to kill herself because she was not allowed to see her son, Sephiroth, and she wanted to punish herself for the pain she had caused Vincent. However, she was unable to due to the Jenova cells still in her body, so she went to a nearby cave and trapped herself within the mako crystals there. Vincent awoke on the operating table, and Hojo and Lucrecia nowhere to be seen. Due to Hojo's metamorphose experimentation, this resulted in Vincent's anatomy being altered allowing him to temporarily change his physical form into monstrous enities, this also is the reason Chaos bonded with Vincent so well. Vincent responded to his modified body with both anguish and rage. He believed that this was his punishment for his "sin" at not being able to save Lucrecia. With that, he punished himself further more by putting himself in a coffin in the Shinra Manor basement. Because of Hojo experiment's, Vincent's age remains physically at 27.