The title complex, [Mo-2 (C5H5)(2) (CH3O)(2) (C4H11Si)(2)(NO)(2)], is formed in high yield by treating [CpMo(NO)(CH2SiMe3)(2)] (Cp is cyclopentadienyl) with methanol. The nitrosyl ligands are nearly linear [O-N-Mo 170.1 (4) and 170.1 (5)degrees], with short Mo-N bonds [1.769 (4) and 1.776 (4) Angstrom] and long N- O bonds [1.216 (5) and 1.201 (4) Angstrom]. The central four-membered Mo2O2 ring exhibits an average Mo-O bond length of 2.15 Angstrom.