  We propose a Seiberg duality for a 3d $\mathcal{N}=2$ $Spin(7)$ gauge theory
with $F$ spinor matters. For $F \ge 6$, the theory allows a magnetic dual
description with an $SU(F-4)$ gauge group. The matter content on the magnetic
side is ``chiral'' and the duality connects ``chiral'' and ``non-chiral'' 3d
gauge theories. As a corollary, we can construct a Seiberg duality for a 3d
$\mathcal{N}=2$ $G_2$ gauge theory with fundamental matters.
