In this paper, nanoparticles of M- type strontium hexaferrite doped with cobalt SrFe_12-xCo_xO₁₉ (x= 0-2) were synthesized via sol– gel technique. Structural and morphological properties of the samples were analyzed by X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FT- IR) and scanning electron microscopy (SEM). The XRD results showed that all of the samples of SrFe_12-xCo_xO₁₉ with x≤0.5 were single-phase. It seems that the Fe³⁺ ions are substituted by Co²⁺ ions in the crystallographic sites of the SrFe₁₂O₁₉ structure, but for the samples with x>0.5, the phase of CoFe₂O₄ is appeared in the samples and suggests that the Co²⁺ ions also make distinct phase in the samples. The value of the lattice constant a is almost kept unchanged but that of lattice constant c decreases with increasing dopant contents. The FT- IR frequency bands in the range of 560–580 cm^-1 and 430– 470 cm^-1correspond to the formation of tetrahedral and octahedral clusters of the metal oxides in ferrites, respectively.