Ni-doped TiO₂ nanoparticles were synthesized by the non-hydrous complex-polymer sol–gel method. Titanium isopropoxide was used as precursor and acetyl acetone (AcAc) and citric acid were used as polymer and complex agent, respectively. A series of Ni_x: Ti_1−xO₂ samples withx=0.01, 0.03, 0.05 and 0.10 were prepared and subsequently annealed at 400, 600 and 800 °C. The structural and magnetic properties of Ni_x: Ti_1−xO₂ were studied by means of x-ray diffraction (XRD) and dc magnetometery. Samples annealed at 400 °C attained a particle size of 12 nm with structural phases of anatase, rutile and cubic NiO. From the blocking temperatures of the zero-field-cooled and field-cooled measurements, similar particle sizes (as from XRD) were obtained. The presence of ferro- and antiferromagnetic (AFM) interactions further confirms that the particles have different structural compositions. At 800 °C the particles have grown to about 30 nm with either a rutile or NiTiO₃-type structure. The presence of NiTiO₃ is also seen in the magnetic measurements, which show the characteristic AFM peak at 23 K.