  Let $\mathfrak{g}$ be a reductive Lie algebra over an algebraically closed,
characteristic zero field or over $\mathbb{R}$. Let $\mathfrak{q}$ be a
parabolic subalgebra of $\mathfrak{g}$. We characterize the derivations of
$\mathfrak{q}$ by decomposing the derivation algebra as the direct sum of two
ideals: one of which being the image of the adjoint representation and the
other consisting of all linear transformations on $\mathfrak{q}$ that map into
the center of $\mathfrak{q}$ and map the derived algebra of $\mathfrak{q}$ to
$0$.
