The synthesis and structural characterization of rare earth alkoxides with thiophene-based substituents are presented. Monomeric metal thienylmethoxides have been prepared by aminolysis reactions between M[N(SiMe3)2]3(M = Y3+, Nd3+, Er3+) and the structurally characterized tertiary alcohols HO-C(C4H3S)3(1) or HO-C(C8H5S2)3(2). The metal alkoxide derivatives of these thiophene-substituted alcohols have been isolated as air-sensitive base adducts, their molecular structures being investigated by single-crystal X-ray crystallography. The coordination spheres around the metal centres are distorted trigonal-bipyramidal for the yttrium thienylmethoxides Y[OC(C4H3S)3]3(thf)2(3a), {Y[OC(C4H3S)3]3(thf)2}·toluene (3b), Y[OC(C4H3S)3]3(py)2(4a), {Y[OC(C4H3S)3]3(py)2}·toluene (4b) and Y[OC(C8H5S2)3]3(thf)2(5). An almost tetrahedral geometry has been detected for Er[OC(C8H5S2)3]3(thf) (9), whereas an approximately octahedral geometry was found for {Nd[OC(C4H3S)3]3(thf)3}·thf (6), {Nd[OC(C8H5S2)3]3(thf)3}·4thf (7) and Er[OC(C4H3S)3]3(thf)3(8).