We study a simplified scenario in the next-to-minimal supersymmetric standard model with a split electroweak spectrum, in which only the singlino and Higgsinos are light and other superpartners are decoupled. Serving as a dark matter candidate, a singlino-dominated neutralino (chi) over tilde (0)(1) should have either resonant annihilation effects or sizable Higgsino components to satisfy the observed relic abundance. The sensitivities of LHC searches and dark matter detection experiments are investigated. With an integrated luminosity of 30(300) fb(-1), 3l + is not an element of(T) and 2l + is not an element of(T) searches at the 13 (14) TeV LHC are expected to reach up to m((chi) over tilde 10) similar to 150(230) GeV and m((chi) over tilde 20,(chi) over tilde1 +/-) similar to 320(480) GeV. Near future dark matter direct and indirect detection experiments are promising to cover the parameter regions where collider searches lose their sensitivities.