  The first observation of the decays $J\!/\!\psi \rightarrow \bar{p}
\Sigma^{+} K_{S}^{0}$ and $J\!/\!\psi \rightarrow p \bar{\Sigma}^{-} K_{S}^{0}$
is reported using $(10087\pm44)\times10^{6}$ $J\!/\!\psi$ events recorded by
the BESIII detector at the BEPCII storage ring. The branching fractions of each
channel are determined to be $\mathcal{B}(J\!/\!\psi \rightarrow \bar{p}
\Sigma^{+} K_{S}^{0})=(1.361 \pm 0.006 \pm 0.025) \times 10^{-4}$ and
$\mathcal{B}(J\!/\!\psi \rightarrow p \bar{\Sigma}^{-} K_{S}^{0})=(1.352 \pm
0.006 \pm 0.025) \times 10^{-4}$. The combined result is
$\mathcal{B}(J\!/\!\psi \rightarrow \bar{p} \Sigma^{+} K_{S}^{0} +c.c.)=(2.725
\pm 0.009 \pm 0.050) \times 10^{-4}$, where the first uncertainty is
statistical and the second systematic. The results presented are in good
agreement with the branching fractions of the isospin partner decay $J\!/\!\psi
\rightarrow p K^- \bar\Sigma^0 + c.c.$.
