  Recently the ATLAS experiment has reported 3.0 sigma excess in an on-Z signal
region in searches for supersymmetric particles. We find that the
next-to-minimal supersymmetric standard model can explain this excess by the
production of gluinos which mainly decay via $\tilde{g} \to g
\tilde{\chi}^0_{2,3} \to g Z \tilde{\chi}^0_{1}$ where $\tilde{\chi}^0_{2,3}$
and $\tilde{\chi}^0_1$ are the Higgsino and the singlino-like neutralinos,
respectively. We show that the observed dark matter density is explained by the
thermal relic density of the singlino-like neutralino, simultaneously. We also
discuss the searches for the Higgs sector of this scenario at the Large Hadron
Collider.
