The Hannah Montana 20th Anniversary Special is a one‑night TV special , not a full series, and it runs roughly feature‑length (about an hour to an hour and a half) as a single program rather than multiple episodes.

What the special is

  • It is a standalone anniversary special released on Disney+ (and also promoted for Hulu in some regions) on March 24, 2026, marking 20 years since the original series premiere.
  • The format centers on an extended, in‑depth interview with Miley Cyrus hosted by Alex Cooper, filmed in front of a live studio audience, with archival clips and recreated sets.

How long it is (practical answer)

  • Official announcements focus on the date, format, and content, but describe it as a single “special” airing like an event, which in Disney+ terms almost always means a one‑off episode in the 60–90 minute range, not a multi‑episode season.
  • There is no indication of multiple parts, weekly drops, or season‑style runtimes; it is consistently marketed as a “20th Anniversary Special” similar to other Disney or sitcom reunion specials that take up a single evening slot.

Given current public info, “how long is Hannah Montana 20th anniversary” = one feature‑length reunion/special (around an hour‑plus), airing as a single program on March 24, 2026.