Katherine Anne "Kitty" Walker McCallister is a fictional character on the primetime show Brothers & Sisters. She is played by actress Calista Flockhart. In a two-part 2010 episode, actress Kay Panabaker portrayed a teenage Kitty Walker in flashback sequences set in 1986.

Kitty Walker is the second eldest of the Walker family, born in late September 1968, although she is the first child of William and Nora (as Sarah Walker was not William's biological child). Kitty shared the conservative beliefs of her father, William, and brother, Tommy. Being Republican, Kitty always clashed with her mother, Nora, who is more liberal. Even though they love each other, their relationship is somewhat complicated.

One of the reasons for their misunderstanding was because of younger brother Justin. Kitty supported his decision to join the army whereas Nora was completely against it, especially after Justin was deployed to Afghanistan. From that point until Kitty's return to Los Angeles the two had barely spoken to each other. Until she returned for a visit for her birthday, Kitty had not been home in several years. She had been living in New York City, and witnessed the fall of the Twin Towers during the September 11 attacks.

Kitty quit her job in New York City as a radio host after she was offered the opportunity to be a part of the political show (Red, White and Blue) in Los Angeles, despite the fact that her then fiancé, Jonathan, didn't want her to. Unable to work things out, they broke up.
After the sudden death of her father, Kitty discovered, along with the rest of the Walker family, that her father had been cheating on her mother and had embezzled money from the company pension fund, putting the family business at risk. Feeling betrayed and vulnerable, Kitty slept with cohost Warren Salter, further complicating things with Jonathan, who wanted to reconcile with her. Soon after, they ultimately decided it was for the best if they broke up permanently. Jonathan returned to New York. Kitty was therefore free to pursue an affair with Warren but he was hesitant, as he was already involved with his young assistant, Amber. Warren finally asked Kitty out, and she accepted on the condition that he set things straight with Amber. When Kitty discovered that he didn't do so, she realized they didn't have a future together.

When Kitty's brother Justin was called to fight in Iraq, she asked one of her guests, Senator Robert McCallister, for his help, but he refused. After another failed attempt to make him change his mind, Kitty apologized in front of her audience. Even though she admitted she had made a mistake, she didn't regret it and decided to leave the show. Robert was nonetheless impressed by her frankness. After much persuasion from Robert, Kitty became his communications director. Even though it was obvious that they were attracted to each other, Kitty was reticent at first, wanting to take a "man fast". The two of them nevertheless started dating soon after. Most recently after the campaign helicopter that she and Robert were scheduled to fly on crashed, Kitty asked McCallister to marry her. Later, the Senator proposed and Kitty accepted.

In Season 2, Kitty continues to plan her wedding to Robert, but when she discovers she is pregnant, the wedding is pushed forward to save the Senator from scandal of having a child out of wedlock. When Kitty eventually miscarries her child, the wedding is put off. After Kitty and Robert marry, their main goal is to have another child; after in vitro fertilization fails, the couple decide to look at adoption. Kitty is also revealed to have written a tell all book about the campaign with Robert and calls in an old friend, Isaac Marshall (played by Danny Glover) to help with the press and Robert's political image. When brother Kevin marries Scotty at the end of the season, it's Kitty who performs the ceremony.

In Season 3, Kitty and Robert are married and starting the adoption process. She asks Sarah to write a recommendation for her and Robert. However, Sarah asks Nora to do it as she doesn't have time. Kitty, suspicious, questions Sarah about the letter and finds out that Nora wrote it, leading to a slight rift between them. Sarah then writes the letter.

Later, Robert tells Kitty that he has heard rumours that someone in his administration has written a book about his failed presidential campaign. It is revealed that Kitty wrote the book and accidentally leaves it at her mother's home. Nora and Justin read the book and tell the others. They read the book and see that Kitty is talking about them negatively. Kitty and Robert then have them all over for a regular Walker dinner for the social worker. The dinner goes horribly, Nora spills water on the social worker, who leaves. Nora and Kitty then get into an argument. Robert, to everyone's surprise, stands up to Nora and defends Kitty. She explains that she used her family to describe certain aspects about the typical voter. Robert, who is slightly angry about the book, reads it and tells her it's brilliant. However, if Kitty publishes it, she will have to resign as his Communications Director. In the episode "Bakersfield", Kitty is upset because Robert told her he was going to Washington but, in fact, went to Iraq to see the effects of the war. She is initially hurt, fearing he will always put his career ahead of his family. While Robert is away, Kitty gets a call from the adoption agency with the news that a woman who is six months pregnant would like them to have her child. When she calls Robert with the news, his overjoyed reaction persuades her to forgive him.