Santana is introduced alongside Quinn and Brittany as one of the three most popular cheerleaders at the fictional William Mc Kinley High School in Lima, Ohio, where the show is set.She joins the school's glee club, and soon is spying on it for Sue Sylvester (Jane Lynch), coach of the cheerleading team the Cheerios.Santana is briefly banished from New Directions for disloyalty, and though she is soon allowed to return, she leaves again to join Mercedes in a newly formed all-girl glee club, the Troubletones, and convinces Brittany, who is now her girlfriend, to come with her.In "Mash Off", Santana pushes the growing rivalry between the clubs to a new level by bullying Finn and Rory.When her supposed apology to Finn becomes another stream of insults, he accuses her of being a coward for tearing other people down because she can't admit that she's in love with Brittany, thus outing her in a crowded public hallway.They are overheard, and Santana's now-revealed lesbianism is used in an "attack" ad against Sue by one of her opponents in the congressional election campaign.When the two are accused of giving Sue the New Directions set list for their first show choir competition, Santana defends herself and admits that she has come to enjoy participating in the club.After Quinn is kicked off the cheerleading squad due to her pregnancy, Santana takes over as head cheerleader.
This storyline has been positively received by critics.
Brittany comforts her, and encourages her to embrace her true identity.
In season three, Santana and Brittany rejoin the Cheerios, and Sue appoints Santana co-captain along with Becky Jackson (Lauren Potter).
Brittany begins to date club member Artie Abrams (Kevin Mc Hale), which piques Santana's jealousy.
She briefly quits the glee club with Brittany and Quinn when Sue demands that they choose between being in glee club and being cheerleaders, but Finn convinces them to reverse their decision, and they quit the Cheerios instead.