At the start of Buffy the Vampire Slayer in 1997, the main cast was mostly in their 20s and early 40s in real life, even though many played teenagers.

Main cast ages

Actor| Character| Approx. age at series start
---|---|---
Sarah Michelle Gellar| Buffy Summers| 19 4
Nicholas Brendon| Xander Harris| 25 4
Alyson Hannigan| Willow Rosenberg| 22 4
Charisma Carpenter| Cordelia Chase| 26 4
David Boreanaz| Angel| 27 4
Anthony Stewart Head| Rupert Giles| 42 4
Kristine Sutherland| Joyce Summers| 41 4
Robia LaMorte| Jenny Calendar| 26 4
Mercedes McNab| Harmony Kendall| 16 4

What stands out

  • Sarah Michelle Gellar was close to Buffy’s teen age, but several classmates were noticeably older in real life.
  • Anthony Stewart Head was the only major adult cast member who was already well into his 40s.
  • Mercedes McNab was the youngest of the group listed here, at 16 during the first season filming period.

Context

The show’s first season was filmed from September 1996 to January 1997, so these ages reflect the cast during that production window. That age gap is one reason the show still feels a little surreal when you rewatch it now.