  Using $(27.12 \pm 0.14) \times 10^{8}$ $\psi(3686)$ events collected with the
BESIII detector at BEPCII, the decay of $\psi(3686) \to \Omega^- K^+
\bar{\Xi}^0 +c.c.$ is observed for the first time. The branching fraction of
this decay is measured to be $\mathcal{B}_{\psi(3686) \to \Omega^- K^+
\bar{\Xi}^0 +c.c.}=(2.78 \pm 0.40 \pm 0.18 ) \times 10^{-6}$, where the first
uncertainty is statistical and the second is systematic. Possible baryon
excited states are searched for in this decay, but no evident intermediate
state is observed with the current sample size.
