In this research, mixtures of barium ferrite (BaFe12O19) and titanium oxide (TiO2) powders were subjected to intensive milling to produce BaFe12O19/TiO2 nanocomposites. The effect of milling time and titanium oxide content on magnetic properties and microwave reflection loss of the samples were investigated by XRD, SEM, TEM, VSM and Microwave Network Analyzer. XRD results revealed that a nanocomposite forms after 10 h of milling. The average crystallite size of BaFe12O19 in the mixture with 50% titanium oxide was 83 and 13 nm in 10 and 40 h milled samples. The coercivity decreased from 2411 to 1156 Oe and saturation magnetization decreased from 26.0 to 15.2 emu/g after 20 h milling of the initial BaFe12O19 with 50% TiO2. The microwave reflection loss of BaFe12O19 increases by addition of TiO2 and processing the mixture via mechanical milling. Microwave reflection loss analysis showed that by increasing the milling time to 20 h, the reflection loss increases in major part of the X band frequencies. The reflection loss of BaFe12O19 with 35% TiO2 after 20 h milling reaches to maximum value of −10.7 dB at 11.5 GHz in the X-band. The reflection loss of the samples with 35% TiO2 milled for 20 h showed that sample with 3.7 mm is at/near to the matching thickness. The effect of particles morphology on microwave reflection loss was also discussed.