What is the best glue to frame a mirror? Help!

Wood glue is the best to glue wood, or Gorilla glue, as it works its way into the crevices. I would also suggest using brads or short staples as added support. You can shoot them into the back side of the frame once you have it glued and clamped

E6000. I assume you want to frame a mirror that is already on a wall like a bathroom mirror.

E6000 will glue almost anything! Great stuff. Good luck.

if you're joining wood to wood, I'd use a wood glue and braces to keep the joints snug while curing -- ELMERS makes a great wood glue ...