Solid solutions of the (1 – x)BiFeO[3]– [x]NdCoO[3] system were synthesized by a solid-state reactions method. Peculiarities of the influence of isovalent substitution in BiFeO[3]of Bi {3+} , Fe{3+} ions by Nd {3+}, Со{3+} ions on the crystal structure, magnetization and thermal expansion of the forming solid solutions Bi[1-x]Nd[x]Fe[1-x]Co[x
O[3] are fixed. It is shown that the substitution up to 2% of Bi{3+}, Fe{3+} ions in BiFeO[3] by Nd{3+}, Со{3+} ions leads only to the partial destruction of the antiferromagnetic ordering of the Fe{3+} ions magnetic moments. According to the results of the magnetic properties investigation it is found that magnetic properties of the samples Bi[1-x]Nd[x]Fe[1-x]Co[x]O[3](0.05 ≤ х ≤ 0.15) are due to the coexistence of the antiferromagnetic and ferromagnetic phases but the samples Bi[1-x]Nd[x]Fe[1-x]Co[x]O[3](0.80 ≤ х ≤ 1.0) reveal paramagnetic properties