Bledel was born to an Argentine father, Martin Bledel, and a Mexican mother of French and German descent, Nanette Dozier; and has a younger brother, Eric David Bledel. Her native language was Spanish. Her parents encouraged her to try community theater at the age of eight to overcome her shyness. The aspiring actress subsequently appeared in local productions of Our Town and The Wizard of Oz before being scouted at a local mall and given work as a model.

She studied at the Page Parkes Center for Modeling and Acting, and was a film major at NYU's Tisch School of Arts for one year before getting the role of Rory Gilmore. In 2002, she was voted one of People magazine's "Hottest Stars Under 25". Among her earliest film appearances was an uncredited role as an extra in Rushmore, which was shot in her hometown

Bledel made her debut on TV in the Gilmore Girls series in 2000, and it is also the show for which she is most famous. She plays Lorelai "Rory" Leigh Gilmore, the daughter of single mother Lorelai Victoria Gilmore. Initially, Rory was a high-school student living with her mother, but she's since moved on to college at Yale University.

She has stated that she feels she can relate in some ways to Rory, both when it comes to some personal traits and her relationship to her own parents. She also sees the family structure and mother-daughter relation on the show as something that a lot of people could relate to.

Bledel was cast for the role of Becky, a prostitute in Old Town, in the movie Sin City. The character Becky was a shift from Bledel's previous TV and film characters. "She's a very professional prostitute. She carries a gun and she kicks ass," (although her character did neither) said Bledel of Becky.

Despite her tough and precocious exterior, Becky gives the impression of being the young and insecure one among the women of Old Town, because of her young appearance and her close relationship to her mother, from whom she keeps her profession a secret.

The movie is shot almost entirely in black and white, with splashes of colour here and there, such as a red dress, blood or an entirely yellow evil character. In Becky's case, it was her eyes that kept their colour, as director Robert Rodriguez claimed that he found Bledel's eyes to be "so amazing I had to keep them blue in the picture...".