The local atomic structures, the magnetic properties and their interrelationship have been investigated for Y_xNi_100−x (x=14, 25 and 40) amorphous alloys prepared by sputtering. The nearest neighbour Ni–Ni and Y–Ni correlations have an asymmetric distribution in Y₁₄Ni₈₆ amorphous alloy. The structural parameters indicate that the arrangement of Ni atoms around Y atom is similar to that in Y₂Ni₁₇ and YNi₅ compounds. On the other hand, the local structure in Y₂₅Ni₇₅ amorphous alloy is different from that in crystalline counterpart YNi₃. The high degree of atomic short-range order in the Y₁₄Ni₈₆ amorphous alloy plays an important role in the onset of ferromagnetism. The local atomic structure in the Y₂₅Ni₇₅ amorphous alloy is close to a random-packing type, and hence the ferromagnetism is not established in contrast with the crystalline counterpart YNi₃. The influence of spin fluctuations on the magnetic properties is clearly observed in high Ni concentration ranges. The relation between the temperature T and the magnetization M exhibits a linear relation of the form in M²–T^4⁄3 in the vicinity of the Curie temperature. At lower temperatures, however, M² varies with T² because of the longitudinal spin fluctuations.