The aim of the presented paper is to study an influence of replacement of Fe atoms by Si atoms in quasibinary Sc(Fe1−xSix)2 Laves phases on their structural and magnetic properties. Powder X-ray diffraction (XRD) and neutron diffraction (ND) measurements carried out at different temperatures from 4.3 K up to about 700 K revealed that samples were single phase with cubic C15 structure for Si concentration x from 0.05 to 0.20 and hexagonal C14 structure for higher concentration. The results of 57Fe Mössbauer measurements showed that the Sc(Fe1−xSix)2 compounds with x ≤ 0.30 are ferrimagnetic at 4.3 K. At temperature 80 K in the samples with x = 0.20 and 0.30, a magnetic cluster spin-glass state has been observed, as ferrimagnetic long-range order disappears. Such picture was supported by the results of ND measurements carried out at 8 K, which confirmed the lack of long-range order for x above 0.10 and an occurrence of hyperfine field distributions in the corresponding Mössbauer spectra. At room temperature, samples with x ≥ 0.20 became paramagnetic. A substitution of Si atoms for Fe ones leads to a decreasing of mean values of hyperfine magnetic fields in samples under investigation. From the neutron diffraction pattern analysis of Sc(Fe0.90Si0.10)2Fe magnetic moment was determined as to be equal to 1.5 μB at 8 K. Combining this result with a value of hyperfine magnetic field on 57Fe probes, the hyperfine coupling constant A in Sc(Fe0.90Cu0.10)2 phases is estimated at about 11.6 T/μB at 8 K.