The youngest child of Stephen and Beth Logan, as a teenager, Katie Logan suffered from horrible acne. Feeling sorry for her, her older sister Donna convinced a good friend, Rocco Carner, to ask Katie out. He did, and Katie was immediately smitten with him.

When she caught him kissing Donna, she was furious with Donna for going after someone she viewed as her boyfriend. Katie and Rocco continued to see each other, but Katie didn't realize that he was actually interested in Donna and not her. She found an engagement ring in his pocket one day and was thrilled to think it was for her, but was devastated after he told her that he had actually bought it for Donna. It was then that she decided to put Rocco in the past and began dating Kurt, one of her classmates at college.

Katie was happy when an anonymous tip led her and Donna to find their father in Arizona. She wanted more than anything to have him stay in Los Angeles with the family, and was thrilled when her parents reunited and moved together to Paris. For a number of years, Katie was relatively off the canvas, but would arrive in town occasionally to babysit her eldest sister Brooke's children. She also bused tables at Insomnia.

When Donna was about to marry Thorne, Katie returned to town for the wedding, and soon overheard Donna admitting that she wasn't truly in love with Thorne. When Katiee confronted Donna, Donna admitted the truth, yet had no plans on telling Thorne. Katie told Thorne herself, and he called off the wedding.

Once Katie's return to L.A. became permanent and after her sister Donna began a relationship with Eric, the Forrester patriarch, flourished, Katie began working at Forrester Creations. She assumed the role of head of Public Relations, which established her as another driving female force--not to mention, another Logan woman--within the company. Initially, there seemed to be a possible spark between Katie and Thorne, but their relationship never evolved into anything romantic.

Katie also had a hand in clearing her father for the attempted murder of Stephanie Forrester. She, along with Jake MacClaine, found a tape exonerating Stephen from the crime. The tape revealed the true shooter to be Storm, her brother, who had been nurturing years of resentment and anger against the Forrester matriarch, especially for her hand in their father's departure. Once the truth was revealed, Katie reasoned with Stephanie and ultimately convinced her not to press charges against Storm so their family could finally heal from all the hurt caused by the Forresters through the years.

Katie also became very close to her niece Bridget at that time. She knew Bridget still had some latent feelings for her ex-husband, Nick, and pushed Bridget to pursue him once more. Katie also befriended him, slowly planting seeds in his mind about a reunion with his ex-wife. Once Brooke was revealed to be the biological mother of Nick's son, Katie insisted on helping him babysit, something she had done for her sister over the years. Spending so much time with Nick, Katie ultimately developed feelings for him, which left her in a precarious situation. While she never intended to hurt Bridget, Katie and Nick's attraction towards one another became undeniable.

After Storm experienced a downward spiral, he became fascinated with Ashley Abbott, who had once been engaged to Ridge Forrester. One night, Katie, because of her brother's erratic behavior, visited Ashley. Storm, brandishing a gun, was inside Ashley's house and Katie stomped in, thinking she could persuade her brother not to harm Ashley. The two fought for the gun and Katie was shot in the chest. She was rushed to the hospital, where it was announced she would need a heart transplant to survive. Guilt-ridden, Storm shot himself in the hospital, in order to provide a heart to save his baby sister. His suicide was a great and long-lasting loss to the Logan clan.

After the transplant, Katie moved in with Bridget and Nick. When Katie showed signs of organ rejection, Bridget asked Nick to show her the time of her life by making her experience things she never had before. It was then that Katie and Nick became intimate when he took her to Catalina Island, although it wasn't revealed immediately that they had sex. Once Katie's health became more stable, Bridget and Nick married, with Katie officiating the ceremony. A while after this, Katie found out she was pregnant with Nick's child after having a routine checkup. When Bridget found out that Katie was pregnant with her husband's child and that her aunt had betrayed her, she left Nick and let him pursue his relationship with Katie.

Katie's relationship with Nick seemed to thrive once it was out in the open. Although Jackie initially encouraged Nick and Katie's relationship, the relationship did not manage to retain her stamp of approval. Jackie constantly reminded Katie of the pain she had caused Bridget, especially after Bridget had saved Katie's life. Katie miscarried early on in the pregnancy and her relationship with Nick became strained because Nick was wary of committing to Katie, due to his mother's disapproval and his unresolved feelings for Bridget. Nick rekindled his romance with Bridget, who had taken a job where she worked alongside Nick as the head designer at Jackie M.

Katie's romantic life did not remain calm for long, as she started dating bad boy Bill Spencer shortly after his failed stint at romancing her sister, Donna. Bill and Katie's romance was unexpected, as Bill was seen as the enemy trying to steal away Forrester Creations from the Forresters--and Logans. After hooking up with Bill, Katie was appointed the new CEO of Forrester Creations, a newly acquired division of Spencer Publications. Bill's motives towards her were unclear to Katie, especially after she saw the DVD that Bill Spencer, Sr., had left his son, asking Bill, Jr., to take down Eric Forrester, and Donna and Brooke Logan, after what they did to the woman he truly loved, Stephanie Forrester. Katie got Bill's word that he was not using her to pursue a vendetta against the Forresters. The two of them got married in Katie's old neighborhood, with their nearest and dearest alongside them.