Microstructural and magnetic properties of BaFe12-xNbxO19 (0.0 <= x <= 0.1) nanohexaferrites (NHFs) have been investigated intensively in this work. The Ba NHFs are synthesized through sol-gel auto-combustion route. The formation of single phase Ba NHFs, in different samples are confirmed by XRD powder patterns, scanning electron microscopy and Fourier Transform Infrared spectroscopy. The magnetic properties of BaFe12-xNbxO19 (0.0 <= x <= 0.1) NHFs were performed at room and low temperatures and discussed in detail. The analysis of hysteresis loops divulged that the different products display hard ferromagnetic behavior at different temperatures. The deduced values of saturation magnetization (M-s), remanence (M-r), magneton number (n(B)) and magneto crystalline anisotropy constant (K-eff) are reduced for lower Nb content and then increased with further increasing the Nb content, reaching a maximum values for BaFe12-xNbxO19 (x = 0.1) nanohexaferrite. The coercivity (H-c) and intrinsic coercivity (H-ci) are diminished for lower x and are comparable to that of pristine one for higher x. The squareness ratio (M-r/M-s) are fluctuating between 0.50 and 0.55, implying the uniaxial anisotropy for different BaFe12-xNbxO19 nanohexaferrite.