A mobile electronic device holder includes an upper holder frame shell, a bottom holder frame shell attached to the bottom side of the upper holder frame shell, three first clamping members respectively slidably mounted in respective sliding ways of the bottom holder frame shell for holding a mobile electronic device, a gear wheel rotatable to move the first clamping members in and out of the upper and bottom holder frame shells, a retractable second clamping member slidably mounted in one sliding way of the bottom holder frame shell and adjustable to one of a series of length.