Elena becomes a vampire at the end of season 3 and fully turns in the season 4 premiere of The Vampire Diaries.

Quick Scoop

  • The key turning point is the season 3 finale , episode 22, titled “The Departed.” Elena drowns in a car accident while unknowingly having vampire blood in her system, which starts her transition.
  • She wakes up in transition between human and vampire right after this, having technically died with vampire blood in her veins.
  • Elena completes her transformation into a full vampire in season 4, episode 1, “Growing Pains,” when she drinks human blood and accepts her new state.
  • Within the story, she had been secretly treated with Damon's vampire blood by Dr. Meredith Fell to heal an earlier injury, which is why her death triggers the change.
  • This marks a major shift for the show’s dynamics and for Elena’s relationships, as she spends seasons 4–6 as a vampire before later taking the Cure to become human again.

So, if you’re just trying to time your watch party: the “becoming a vampire” twist hits in S3E22 , and the “Elena as an actual vampire on screen” starts in S4E1.

TL;DR: Elena becomes a vampire when she dies in the season 3 finale (“The Departed”) and fully turns in the season 4 premiere (“Growing Pains”).

Information gathered from public forums or data available on the internet and portrayed here.