Jennifer Walters grew up in a happy home in Los Angeles, although her mother died when Jennifer was at an early age. Growing up to be a successful prosecuting attorney, she was run off the road by the criminals she was investing. Her cousin, Bruce Banner, also known as the Hulk, saved her life by performing an emergency roadside blood transfusion. Jennifer found herself able to transform into the giant She-Hulk, but never restricted by the split-personalities of her brother, Jennifer was able to transform at will and retain her full intelligence and memories. She had a successful run of adventures as She-Hulk, even though her sheriff father distrusted and was constantly hunting She-Hulk. Eventually, She-Hulk found herself unable to transform back into Jennifer, but, after reconciling with her father, never found cause to revert anyway, preferring the adventures she had in her alter ego. Eventually moving to New York, She-Hulk was contacted by the Wasp in a membership drive for the Avengers. She served for a brief stint before being among the Avengers captured by the Beyonder to his "Battleworld" and pitted against similar abducted villains. When returning to Earth, She-Hulk was invited to take the place of the Thing in the Fantastic Four, and she joined them.

During her tenure with the Fantastic Four, the She-Hulk had to prevent a radiation leak in a downed S.H.I.E.L.D. Helicarrier. This radiation exposure apparently mutated Jennifer to the point that she could not transform back into her original form. But this was an agreeable turn of events for her, since she preferred her She-Hulk form anyway. It was revealed much later that the "genetic block" was in fact purely psychological, shortly before a similar block locked her in non-Hulk form. That block proved to be temporary.

After the Fantastic Four , the She-Hulk rejoined the Avengers and joined the staff of District Attorney Blake Tower, where she met Louise "Weezi" Mason, formerly the Golden Age super heroine called the Blonde Phantom; during this period, she discovered that Mason had manipulated Towers into hiring She-Hulk so that Mason could again star in a comic book and thus avoid dying of old age. Mason's husband, also a former comic book character, had passed away three years ago, but other, more popular characters from the era, such as Captain America and Namor the Sub-Mariner, were still around.

She-Hulk was a member of the short lived hero group the Fantastic Force. Later, while doing some legal work for Heroes for Hire, she also went on a few adventures with them and spent some time dating Luke Cage.

Eventually, Jen returned to the Avengers and remained with the team for some time. On one adventure, the She-Hulk was exposed to fellow Avenger Jack of Hearts radiation powers causing Jen to lose control of the savage side of her personality. She injured several Avengers and went berserk in Bone, Idaho, virtually destroying the whole town. With Jen's fear and rage at an all-time high the assembled Avengers couldn't stop her.

Only the Hulk himself was able to slow her down until Jack of Hearts was able to use his powers to balance her Gamma levels and she regained control over her savage side. Jen's normal personality was restored for a time but her worst fear came true when Scarlet Witch went temporarily insane and used her magic to cause Jen to lose control again. This time, she nearly killed Captain America and tore the Vision in half with her bare hands.

Although she had been manipulated, She-Hulk was devastated at her part in the Vision's death and the destruction of the town of Bone, Idaho. Ashamed, She-Hulk quit the Avengers to resume her law career and spend more time as plain Jennifer Walters.