A cross-linkable nitrile rubber composition comprising a nitrile rubber (A1) including an α,β-ethylenically unsaturated nitrile monomer unit and having iodine value of 120 or less, silica (B1) having CaO value determined by X-ray fluorescence composition analysis of 0.5 wt % or more, and a crosslinking agent (C1). According to the present invention, a cross-linkable nitrile rubber composition, capable of giving a highly-saturated cross-linked nitrile rubber having excellent mechanical properties such as elongation and small compression set, and excellent in workability, and a cross-linked rubber obtained by crosslinking the rubber composition can be provided.