Upon the release of the second season, Blair was described by the television series' creators as the "chess queen" from Gossip Girl. Most of Blair's storyline during this season revolves around her love-hate relationship with Chuck Bass, with this relationship being referred to by People magazine as "the heart of Gossip Girl". As a competitive relationship with Serena emerges, Blair forms an unexpected friendship with Jenny, who tells Blair how hard they both work to achieve their goals while Serena achieves everything easily. During their admissions interviews at Yale University, Blair and Serena apologize for their misdeeds and renew their friendship. In the episode "O Brother, Where Bart Thou?", Chuck is devastated by the news of his father's death, leading Blair to offer her unconditional support and tell him she loves him. Chuck initially avoids Blair's advances, but ends up going to her looking for comfort. However, the two stop seeing each other because of Chuck's uncle, Jack Bass, who convinces him of his inability to commit and maintain a serious relationship. . After being rejected from Yale University, Blair receives unexpected encouragement from Nate. She is later admitted to New York University and her competitiveness with Georgina is eventually renewed. During the season finale, Blair crowns Jenny as the new "queen bee" of Constance Billard School, where she attended high school. At the end of the season, Blair discovers that Chuck had sex with Vanessa Abrams. Chuck then decides to leave for Europe. He later returns to New York City and reconciles with Blair saying he loves her, and the two finally commit to a serious relationship. Gossip Girl
In season three, Blair joins Vanessa, Georgina, and Dan at New York University. Much of Blair's storyline this season focuses on her inability to achieve her former position as "queen bee." She has a lot of emotional support from her mother, as well as Chuck. However, she and Chuck break up again when Blair feels he manipulated her in a competition with Jack. After a while, Blair transfers to Columbia University and discovers that Chuck was responsible for her admission. Later, they come together to devise a plan in favor of Lily, Serena's mother and Chuck's adoptive mother. In the season finale, Chuck tries to propose to Blair, but is stopped by Dan, who reveals that Chuck had sex with Jenny, causing Blair to despise him. Two weeks later, Blair and Serena go to Paris to spend the summer together.
In the first chapter of the fifth season, Blair continues planning her wedding to Louis, but begins to find fault with the relationship. It is later revealed that she is pregnant. Blair tells Chuck that the baby is Louis's and that part of her wanted him to be the father. Dan becomes Blair's confidant as it is revealed that he is in love with her, although she remains indifferent to his feelings, stating that there is nothing between them but friendship. Although Blair insists she is in love with Louis, she begins looking for Chuck. The two eventually declare their love for each other before getting into a car accident. Although they both recover, Blair suffers a miscarriage due to the accident. On the wedding day, Gossip Girl posts a video of Blair confessing her love for Chuck. Still, Louis and Blair get married, although Louis tells her that they will have a loveless, sham marriage. She then receives support from Dan, with whom she shares a kiss on Valentine's Day. After this event, Blair finds herself torn between Dan and Chuck. After getting tips on how to annul her marriage, Blair chooses to start a romantic relationship with Dan. At the end of the season, however, after a debate about which love is best — with With Dan she feels safe and with Chuck she feels vulnerable — Blair realizes that she is still in love with Chuck and decides to look for him.
In the first episode of the sixth and final season, Blair and Chuck make a pact to only stay together after achieving their goals. While Blair aims to succeed in running the company Waldorf Designs, Chuck aims to defeat his father, Bart, who was revealed in the fifth season to be alive. Blair works hard to develop her career as a designer at Waldorf Designs, amidst several setbacks, before achieving a successful clothing collection and fulfilling her end of the pact. In the penultimate episode of the season, Bart dies after falling from the roof of a building while trying to attack Chuck, and only Blair witnesses what happened. Later, she marries Chuck seeking the marital privileges in which the wife cannot be forced to testify against her husband, and, in this way, both are dismissed by the police because there is no evidence to accuse Chuck, other than the only witness, Blair, now his wife. When it is revealed that the Gossip Girl blogger is actually Dan Humprey, Blair is furious and says that he ruined everyone's lives, but Serena tells Blair that she is only mad because it was Dan who controlled everything. Blair then assumes that it's all over now and that they can grow up and move on. Dan confirms and says that Gossip Girl is "dead". Five years after their wedding, Chuck and Blair are happy and have a young son named Henry. Blair appears to be successful as director of Waldorf Designs. In her last appearance, Blair appears hand in hand with Chuck as they witness Serena and Dan's wedding in a private ceremony.