  Let $D$ be a weighted oriented graph, whose underlying graph is $G$, and let
$I(D)$ be its edge ideal. If $G$ has no $3$-, $5$-, or $7$-cycles, or $G$ is
K\"{o}nig, we characterize when $I(D)$ is unmixed. If $G$ has no $3$- or
$5$-cycles, or $G$ is K\"onig, we characterize when $I(D)$ is Cohen--Macaulay.
We prove that $I(D)$ is unmixed if and only if $I(D)$ is Cohen--Macaulay when
$G$ has girth greater than $7$ or $G$ is K\"onig and has no $4$-cycles.
