Carrie and Sebastian first sleep together in Season 1, Episode 12, “A First Time for Everything,” of The Carrie Diaries.

Quick scoop

That episode is the one where Carrie hopes for a “first time” moment with Sebastian, and the night builds toward that turning point.

Small note

If you meant their first actual hookup on-screen versus a later reconciliation scene , the show also revisits their relationship in the Season 1 finale, “Kiss Yesterday Goodbye,” where they spend the night together again in a complicated way.