Tifa Lockhart is twenty years old and was born in a small mountain town of Nibelheim, the same town where Cloud was born. She is a very out going and living. She is quick at gaining friends. Cloud and her were only a year apart. However, they were very distance from each other. Along with her friends, she ignored Cloud through most of their childhood. However, one year before Cloud left Nibelheim to become a SOLDIER, Tifa made him promise to come and save her if she was ever in trouble.
At eight years of age, Tifa lost her mother, leaving her upset and very confused. Instead of believing that her mother was dead, Tifa believed she had gone to Mt. Nibel. Tifa heads off to Mount Nibel, and Cloud followed to keep her safe, but Tifa still fell from the rickety bridge in the mountains. Tifa's father arrived at the scene, and finding her hurt, blamed Cloud for leading her to Mt. Nibel. Upset and angry, Cloud swore to become a SOLDIER, like his idol Sephiroth.
A few years later, Sephiroth and a SOLDIER called Zack arrived at her hometown to investigate as well as check out the Mako Reactor in the mountains. They hired Tifa who was a student of Zangan, the town's martial artisst master, as their guide in the mountains. During their journey, Sephiroth discovers the horrible truth of his origins, and loses his mind. He attacks the twon, and burns the city to the ground, heading for Mt. Nibel. Zack follows him into the Mako Reactor. Tifa tries to follow them inside, but a soldier (unbeknownst by her, it is Cloud) stops her. When she eventually manages to get inside, she discovers her father has been killed by Sephiroth. Enraged by her loss, she heads for the Mako Reactor core, but is struck down by Sephiroth. Cloud suddenly appears, and defeats Sephiroth despite being impaled by Sephiroth's Masamune blade, and throws him down into the reactor core. Tifa is severely wounded, and doesn't remember Cloud saving her. After the incident she grows to hate Shinra.
Eventually, she moves to Midgar, and opens a bar called 7th Heaven, which becomes the secret operation for the group called AVALANCHE. Tifa finds a confused and disoriented Cloud in the slums, where he claims to have completed his goal of being a SOLDEIR first class. Together they complete several missions to destroy Midgar's Mako Reactors. However Shinra stops them by dropping the upper plate above Sector 7, effectively killing AVALANCHE and an high amount number of civilians. AVALANCHE members Jessie, Biggs and Wedge are killed in this event.
After discovering Sephiroth's return in the Shinra tower, the party begins to follow him in order to get revenge for Nibelhiem.
Later in Kalm. Cloud decides to tell his unknowing friends the story of his past and Sephiroth, but Tifa is troubled by what she hears. A lot of things he is saying does not match up to what actually happened, and that there are a lot of holes in his story. But she keeps her worries to herself.
When they arrive at Nibelheim, they discover that the town has been rebuilt, and the villagers (who are really actors hired by Shinra to cover up the Sephiroth incident) do not remember Cloud or Tifa ever living there.
At the top of Mount Gaea, Cloud is being controlled by Sephiroth to give him the Black Materia, and falls into the Lifestream. Tifa is elected temporary leader of the player characters while Cloud is gone. He is later found in Mideel, suffering from an overdose of Mako. Tifa stays behind to watch over Cloud, and Cid is elected leader. Later, the friends decide to check up on Cloud, who is not showing any signs of improvement. However, suddenly, the Ultimate Weapon appears, and Mideel is swallowed by the Lifestream, and Tifa and Cloud falls into it. Tifa has now entered Cloud's mind, and together they work through Cloud's painful memories, and uncover the truth about the Nibelheim incident, and brings Cloud back. After their assault on Midgar, they reflect on their past and future.
After the ultimate defeat of Sephiroth, Cloud is stuck on a ledge, and Tifa tries to rescue him. They are ultimately saved by Cait Sith, and escape in Cid's Airship. The omnipotent Meteor, summoned by Sephiroth, looms closer to the earth, but a white light, which is Holy appears and tries to stop Meteor. It fails, however, and Meteor destroys Midgar. Suddenly, the Lifestream appears, and stops Meteor, and the last thing seen before the credits is Aeris' face.