They effectively “start” on Selection Sunday , when the official 68‑team brackets are revealed and fans can begin filling them out.

For March Madness 2026 specifically:

  • Bracket release (Selection Sunday): Sunday, March 15, 2026, with the men’s bracket at 6 p.m. ET and the women’s at 8 p.m. ET.
  • First Four games: March 17–18, 2026 – most bracket contests lock right before the first of these games tips off.
  • Traditional first round (full wall‑of‑TVs chaos): March 19–20, 2026; some casual office pools still use the start of these games as the “last chance” to submit a bracket.

So if you’re asking “when do March Madness brackets start?” in the sense of when you can start filling them out , that’s Selection Sunday evening, March 15, 2026.

If you mean “how long do I have?” then assume:

  • Most major online games (ESPN, Yahoo, CBS, etc.) close entries just before the First Four or at least before the first full Thursday game , so you’ll want your picks locked in by the afternoon of March 19, 2026, at the latest , unless the specific pool says otherwise.

Quick Scoop

  • Brackets “go live” when the field is announced on Selection Sunday (March 15, 2026).
  • Many fans start filling them out that night and tweak them until just before games start.
  • Entry deadlines vary by site or office pool, but aim to submit before the First Four or, at worst, before the Thursday day games.

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