Blaine Devon Anderson is an openly gay student at Dalton Academy and a member of The Warblers, a Sectionals and Regionals rival of New Directions. While Blaine was initially a recurring character, he was promoted to the main cast for the third season. The character is a love interest for Kurt, though, he and Rachel have a brief fling, resulting in Blaine reasserting his identity as gay. He had to leave his own school because of bullying and goes to an all-boys academy and finds acceptance because that school has a no-bullying, zero-tolerance policy." Blaine becomes a role model for Kurt, who develops a crush on him. When he hears Kurt sing "Black Bird" Blaine realizes he reciprocates Kurt's feeling, and later they kiss. At the beginning of season three, Blaine decides to transfer to McKinley to be with Kurt, and joins New Directions. Blaine is injured during a confrontation between New Directions and the Warblers, and has eye surgery to repair the damage. His relationship with Kurt is later strained by Kurt's eagerness to leave for New York after graduation, which would separate the two at least until Blaine graduated the following year, but the two patch things up, and are still a couple at the end of the school year.

At the beginning of his senior year, Blaine becomes the lead singer of New Directions and successfully prompts Kurt to follow his New York City dreams. Blaine successfully runs for senior class president. Kurt inadvertently pulls away from Blaine due to his Vogue.com internship and hectic schedule; distraught, Blaine cheats on Kurt. After confessing to Kurt of his infidelity, Kurt severs all ties. Hunter Clarington, the new captain of the Dalton Academy Warblers, attempts to convince Blaine to return to the Warbler. Blaine becomes conflicted, but Sam Evans ultimately convinces him that, despite having done a bad thing, Blaine is still a good person and an important member of New Directions. Kurt begins to mend their relationship in and they spend Christmas together in New York City, though Kurt is very clear that they are not back together.